Hi Mate,
I Know exactly what your'e going through....I Had the exactly same problem on my P-reg 2.0ltr GTI where the car would start up okay..then at any particular time the oil light would flash and revs would hit zero and cut engine out....Very dangerous if cars are up your arse!!!
After going backward and forwards to garage several times, replacing all plugs,Ht,Dizzy,Rotar arm, Injection cables, Oil sensor, Relays etc.....I Finally took my GTI to an idependant VW/Audi Car specialist and put GTI on his VW Dealer Diagnistic machine....It diagnosed the CRANK SENSOR as the problem...this cost me £145 from Dealers...as he would only fit Genuine Vw parts...however I Believe you can get the part for around £50 non genuine..so far so good, no more embarrassing cut out at main juctions for me!!!.....Hope this info helps...and good luck...Rob.