I had a recent problem with an oil leak, which required a new sump. Whilst at the delaers they said there was a slight clatter from the water pump. I'd not noticed before but it sounds just like the ticking you are experiencing.

The pump is on order, Dealer said it was OK to drive on the exisiting one for now. I'll let you know when work is complete and if it makes a difference.

Cheers

Andy G