Timing advice (URGENT!)

1999 1.4 16v Polo

I had the water pump replaced yesterday (as impellor was spinning and it wasn't pumping water to the heat exchanger for internal cabin heat). I now have heat in the cabin... however... the idle is ever so slightly lumpy, which I'm pretty sure it wasn't before.

As the water pump is powered by the cam belt I suspect the timing is out by a tooth. Is this likely? Would this cause an 'ever so slightly' lumpy idle?

Would appreciate any urgent responses as it's back with the mechanics today and if it could be something else (does the ECU need resettihng after cambelt replacement?) I'd want to save them the bother of checking... and me the possibility of another bill!

Thanks

Edited 8 February, 200818 yr by Sqwim