Not had a lot of dealings with the aftermarket side,the times I have used them ~~ Sean ~~ I think,seems to know his stuff.
However the engine /gearbox building side ~~ Neil Fletcher,I would rate as second to none.Neil has built every Renault Rally engine for me from 1990 until today,had a very trick 5Gt turbo engine with a hybrid turbo gave 208bhp ~~flywheel not only on there dyno,but also one at Bolton.Built a new gearbox for me with a ZF Lsd.Had various valver engines.Now got a Williams engine on throttle bodies,cams etc,I have never had cause to complain.I got a deal from them to build my Rally car,I just supplied a welded and caged up shell.
There might be people,who have not had the same level of service,that I have,although the friends and aquaintenances I have recommended have all been satisfied.
I reckon Neil Fletcher has forgotten more about Renault engines,than I know
,Bit of distance for me to travel,but well worth it as far as I am concerned.Wish they would get there Rolling road,installed again.