probably ignition switch chap, holding main beam on is well known way to bypass a faulty switch

also could be wiring fault, so check the wiring from the ignb switch to the fusebox. if its damaged lucky for you this bit of loom is completely separate so can be replaced on its own.
get down scrappy looking at 90spec mk2, mk3, b3/4 passat, corrado, seat ibiza/toledo etc. basically if it has hazard switch on column then it'll probably work. only exception is polo/lupo as they have a different fusebox i think? take the odl loom in there and compare it to the car you're pillaging it from