Not sure if there classed as running shoes mate but there mega comfy and light on your feet.
I use lacoste Sento's There about £50-£60, Just 1 velcro strap so no messing around tieng up etc and after a while they mould to the shape of your feet so it doesnt feel like youv'e got anything on them, really comfy.
If not them id say Nike Shox Arraw + SL, havnt personally used them but heard they are really good. Can be found on : http://store.nike.com/emeastore/#,en,GB,;stage,prod_grid-309103-309148-144702//160275//0--0/|2
I just noticed you're in S. London, so thought I'd make a suggestion for you. Find a shop called 'Runner's Need' (there's one in Canary Wharf); they're the best shop I've been to for running shoes - they analyse your running style on a treadmill (called 'Gait Analysis'), then find you trainer's that you'll get the most benefit from.
Having the analysis and some top advice (all the people who work in the shop are competitive runner's) is invaluable, as you'll be doing a lot of running in preparation for the Marines, so its worth having the right kit. The trainer's will set you back a few stirling more than if you got some standard running shoes from a local sports shop, but then, if you want quality you have to pay for it. I'm very happy with mine, and they set me back £70.
Right firstly with running shoes, its not so much the brand & how expensive they are, its about whether the suit your style of running. All to often people unknowingly buy the wrong type of running shoes.
If any of you are having any kind of discomfort or pain and you think its related to your running style and running shoes, then i suggest you visit a specialist running shop and ask if they can preform whats known as a 'Gait' analysis. This is were the put you in a pair of neutral running shoes and have you jog on a treadmill for around 30 to 50 seconds whilst recording you.
The recorded footage will the be reviewed, checking your heel to toe foot strike in each stride you take. Depending on your style which can vary from under pronating, over pronating and a neutral stance the shop will advise you on which kinda of running shoe you should be using, then once you know you can check out all the brands and go for something that you like. So not only will you have the brand of shoe you like but it will also benefit your running as its the right type of running shoe for your running style.
I use Brooks GT5 (not for sale anymore) which have served my feet well. Never had blisters, never had shin splints, never felt uncomfortable. I have a wide foot and very very mild pronation and I bought these and by pure luck they're perfect for my style of running!
It'll be a shame to let these go but next if I ever get chance I'll run in Brooks Cascadia 3.