Well, you certainly seem serious about it, so good luck and gods bless all who sail in you

I'd guess that about 90% if not more of UK machines using lipos get them from one of two places; OptiPower through the FRA's discount scheme, for high-end proven performance that you get what you pay for, or Hobbyking for the rest of us plebeians - both can deliver in the UK. Treated well and specced properly I'd imagine the cheaper batteries will do just as well, but I'll let everyone else weigh in!

I think I can visualise the weapon (I'm thinking The Kraken from series 7 but with the extra claw mounted directly to the first one?) but a sketch or drawing or CAD always helps with these things.