Little bit of an update to this.
After having skirmished it a few times. I really did feel it was lacking a bit in the FPS department. With a decent chrono it was making about 465 on average which for an off the shelf kit didn't feel too bad but was hardly what I really wanted from it.
I contacted ASPUK and asked them about the barrel, somethign was itching me about it and I didn't think it was quite as good as it could have been, I wrote a very honest, complimentary but digging email commenting on my FPS results and what I could try and do to improve. ASPUK were really good with me and did admit the barrel can be better and that I may have some better results with an alternative.
I've since purchased a Laylax PSS barrel and that improved my FPS to around 475 on average along with PTFE taping the hop rubber to the new barrel. A nice little boost but still under what I really wanted it to be.
My next move was a bit stupid but ultimately got me to the place where I wanted to be, I saw an Action Army M170 spring on ebay from a UK seller for cheap so bought it on a whim, it was delivered and installed and then chronoing thoruhg it was coming in at 600FPS! Far too much but mad eme question the spring I already had in place, is the SNiper one spring any good at all? Yes it's bedded in but that much?
I fed back my information to ASPUK and raised the question, how good are the S1 springs? Could the AA one I tested be a touch strong or are the S1 springs a touch weak (giving them chance to tell me the AA one was strong)? On this occasion though the email didn't have much praise for anything else in the kit and I can't help but feel the constant want for feedback had ended at this point. I managed to source from AirsoftWorld an AA M150 to directly compare with the S1 spring. So I know that a new spring will perform better than one thats seen 10 games but straight out the box it was hitting 505, 506, 507 for me.
I've finally got the sniper I wanted!