Well found it at last! Checked absolutely everything and found that he previous own had taken a live from the auxillary fused cable (purple) into one of the flasher unit connectors! So it was getting a constant feed. I think he had by passed the hazard switch previously as that was dodgy. But I had changed that for another a couple of years ago! Anyway took the feed out and all fine now.

No idea why it should have taken so long for this to manifest itself but I guess it took a while for my last hazard switch to burn through. Very strange but fingers crossed now.

Thanks for all your help! So Blue Beasty was actually spot on but it wasn't a short, it was deliberate for some reason!

Yeeeaay! Thats 12 useful posts already!