2000 Renault Clio high revving sound

Can't really get involved with dispute between dealer and yourself as not in a position to check vehicle and aware of all facts etc. Only thing I would suggest is asking the dealer why the throttle body , diagnosed as cause of fault and fitted for £423 did not cure the fault . If , as you say ,it was just the same , was part needed ? Or was it the damp in computer all a long ? I'm surprised they gave you the car back with the car in the same condition , was it not tested / checked ? Might be worthwhile asking them for Renault customer services contact number if not getting satisfaction from dealer .
P.s
Best not to mention you have been on to car forum for help / info as they do not like outside parties giving an opinion when not fully involved . I can understand that, as there may be facts I am unaware off .