i guess your in scotland? where's abouts?

i wouldn't have thought temps would reduce power by that much but then i could be wrong

nuermous intercoolers available but it depends on your budget, i run a pace rs500 style intercooler and never had any issues, a few people dont like them as there are better manufactures of these around such as pro alloy or radtec. You will pay a premium for such names so maybe go with what tabs has suggested

if you dont want to buy new, try paul at north yorks rs spares http://www.cosworthrsspares.co.uk/ or pm him off here rs500 registrar