Be careful with britishmilitarysurplus. I've ordered an ubac from them, and it turned out that the sizing is way off. My chest is exactly 112cm so it's Extra Large according to their chart. However the XL ubac was gigantic. It took quite a few emails with photos to convince them to send me a new one if I return the big one. I still had to pay the return P&P. They said that it's not their fault if their supplier gives wrong size (according to their logic it's my fault.)
Otherwise they sell good stuff but the customer service is not very customer oriented...
You could buy a 7.6 lipo bat if you want but would also need a smart charger which costs a bit more.
.2's are usually cheaper than .25's but if youre shooting around 350fps .25 will give you a bit more range. my main AEG shoots about 290 at the moment so I use .2's.
If you have a local army & navy they sell all sorts of surplus military grade clothing.
also if you dont have you should get some boots if youre playing outdoors
I used to live out MK way a while ago.If your looking for army surplus kit, there was a good store in Stony Stratford on the main high street. Might be worth checking it out.