decent mechanic in southend needed?

my renault clio keeps stalling and over revving and guy who sold me it - iffy as hell and moved so cant gte fixed by him,so another mechanic told me its was exhaust paid that,same problem,head gasket- checked and ok, then said coils,so put ignition coil on, then said it could be crankshaft....300 quid later and same problem,loses power driving,stalls in motion or in idle traffic, and over revs.....help!!!!!