Go here for turbos and intercoolers, american though but still cheapish!
Intercooler- £200
T28 Turbo (same bb use for £1000)- £400
Cant see the postage etc adding upto £1100 which is the saving!
For pistons:
http://www.forgedpistons.co.uk/catal...19&man=Renault
They do a 7:5.1 for the williams which offers potential of more boost than just a thicker head gasket
Con Rods And Bolts:
German site, prices are a bit expensive but whats got to be expected i guess, for the sport spec rods it costs about £760 and for the race spec rods its £996
http://translate.google.com/translat...language_tools
All parts on those links are new!