There was a discussion over on Outdoormagic as to whether it was worth getting surplus Goretex or civvy stuff. Someone still serving commented:
'Is there any reason you want surplus kit? I've been issued it all for free and I still buy my own kit since most is crap. '
As a couple of people have already commented, the surplus stuff is going to be heavier than the high street jackets, and its cammo, which is not always a good look in your local high street, and actually not a good idea if someone is trying to find you on a hill! Much as I like surplus stuff, I must admit that the word 'used' generally means 'hammered' (unless its from Endys).
TKMaxx might have what you want (certainly the trousers), or just try Cotswold - you can pick up a (non Goretex) jacket for less than a £100, and if you check out how they rate at OM, you might get a bargain.
3 Peaks sounds great, but don't skimp on the important stuff - a good jacket will make life easier at best, and save your life at worse.
The British Army lights are pretty good (got a pair myself), but their cotton (no wicking), not very warm and don't dry all that well when wet, perhaps the C95's
http://www.endicotts.co.uk/product_info.php?cPath=128&products_id=1230 if your fine with cammo, or TKMaxx craghoppers if not (£20). Good luck!