unless you get a 2nd hand one, tbh imo your best off buying a new genuine part from dave,
whats to say the 2nd hand part wont go wrong in the next few months, least with a new genuine part you know it should last!!
ps i had same problem, and bought a new genuine part from dave!
as someone said there's not really a cheap fix its either take a gamble and buy a 2nd hand one for about 90- 100 quid (if you can find one) or pay 170 for a brand spanker which you know will be right!