First of all, the type of fitness training conducted is vitally important (the word "fitness" being one of the most misused (and abused) words in the English language).
For instance, long distance cycling will get you fit...for long distance cycling. Running will get you fit...for running. The point being that there are activities that are OK for general condidtioning, but it is absolutely vital that you "train for need". In other words, if tabbing ridiculous distances with a bergan is what is required, then that is the type of training to do. The reason for this is that different activities not only demand different muscles in order to perform the activity, but also place the demand on the muscles differently. You might think you are fit because you run/work out a lot, but then the first time you are told to run your arse off with a ruck on your back, you go and get an injury.

Believe me, an injury is the kiss of death on Selection.

You can work around blisters and such like, but an injury - especially a white, fibrous tissue injury - is going to do you in.
So, the order of the day is ... get out and hit the hills with that weight on your back (progressively of course). Cross-graining (as opposed to traversing) is one hell of a good workout. You'll curse it up and down, but it'll be worth it.

Having said all of that, good cardio and strength are also vital as they provide the stamina and core stability needed to keep you going. Abs training is one of the best things you can do to give stability to your spine (apart from back trg).
Luckily, running is the best and most convenient way to gain good cardio, while also having the hidden benefit of strengthening the muscles in the lower torso (esp back and abs).
Next time you are running, just place the palm of your hand in the small of your back as you go along and feel the activity there...amazing! It's the same with your abs!
Hill work (with your bergan) will give you good leg strength, but a few reps on your hamstrings, quads and calves in the gym wouldn't hurt.
Don't look to bulk-up - no Mr Universe ever passed selection!
You need a good combination of strength and stamina. To be honest, power-to-weight ratio exercises are the best thing going for what you need...chin-ups, sit-ups, push-ups, dips, etc.

DO NOT run with weight
Do NOT run with weight

If you were to start selection from no training at all, dependant on your physical size, 6 months of build up should be enough to get you started on the course.

CFT's are never that much fun.To train for them, as long as you have a good level of fitness to start with, you can always get through them with a bit of grit and determination.

A weekend up in the hills walking 30 miles a day at a walk pace will do you much more good than running round the block with a pack on your back.
'bergan run' is a generic term that is being applied to training with a bergan...which IS a good idea, running with a bergan isn't.

Dont believe everything you read or get told.
It is true many Regiment lads can run 10 miles in an hour and some even more, however- endurance is the great leveller of men, the Regiment seeks individuals that can go it alone for very long periods of time. Cardiovascular fitness and CO2 uptake are very important but endurance and stamina are even more important.

The fitness has to be specific to the aim (passing aptitude and serving in UKSF)
Yes, time on the legs is important- it serves you well when you get up the hills by providing you with the base stamina level on which to build your self up.
Picture this- Lance Armstrong spends most of his time training for his next race on a rowing machine and not his bike do you think hes going to win? No.
This is due to adaptation.
The way to improve your 'specific' fitness (in our case Fell walking with weight over ardous terrain) is to increase one of several variables.
These are frequency, duration, and intensity.
Only increase one of these at a time- for example week one training may have 2x 2-3 hour hills with 40 lbs.
To increase (overload) your next week should be either
3 x 2-3 hours 40lb or
2 x 2-3 hours 40lb or
2 x 2-3 hours 45lb
NOT
4x 4-5 hours 55lb

Just don't run with that weight.
Do all of your running without the weight.
Remember 8 miles in 2 hours isn't that hard.

Running-
Do simple fast runs, middle distance, and endurance builders or play about- say run 60 min's but put in a 1 min sprint in every 4- so you would sprint 1 min normal, run 4 min's, repeat till end of run. That builds the speed up sharpish that does.

Motivation is a state of mind. When you are up on the hills, its only your own motivation that pushes you all the way to the next RV in the best possible time. It is so easy to just steadily make it to the next RV and feel OK and only just make the time, but if you make a nav error you don't have any time to recover!

Maximum effort all of the way !!
Push, Push and push some more

How well motivated you are depends on how optimistic you are of success, and how important that success is to you. You have to want it and you have to KNOW deep in your heart that you ARE going to pass, not COULD pass but ARE going to, no two ways about it.
Last thing at night and first thing in morning is the desire, thirst and hunger for it.

Try aim for 8 miles in an hour. Do this once or twice a week + circuits or cycling and plenty of walking. I stress also...walking. Not running about with a house on your back.
As for boots, just see how your first weekend goes and ask your DS for advice(they might know of places you can get boots at a good price).
Cycling, swimming,circuits, mixing it up.

CFT's are never that much fun to train for but as long as you have a good level of fitness to start with, you can always get through them with a bit of grit and determination.

If you have never done any speed march work get a
30lbs bergan on, with trainers and just practice a fast walk. The one thing that many newcomers find is that their shins really ache. A bit of practice at this will not do you any harm.

During selection, runs will be set at a very fast pace (7 min miles) together with lots of beastings in between, firemans lifts, shuttles, baby carries etc etc...runs last between 45-80 mins.

When it comes to tests, the only running test on selection whether its 21, 22 or 23 is an 8 miler cross country to be done in Wales in under an hour. There is a lot of running but no where near as much as people think. More to the point you do not need to run 10 miles in an hour!

have any one got any training advice about upper body strength if its evan required