Rover owners: Water pump removal has beaten me!

Hi Guys, I am in the process of repairing the head gasket on my 2002 1.8 TF and decided to fit a new water pump and thermostat whilst I am in there.

I have removed all of the bolts around the water pump housing but it will not budge - I am reluctant to whack it with a hammer!

I can see what appears to be a locating stud at the bottom of the water pump casing - or has a bolt been sheered in the past? Anyway I do not think the water pump casing is threaded so it should just slide off? Maybe I can see the end of a bolt fitted from the other side but I cannot find it....

I have outlined the item in the attached pics. Any ideas anyone?

Really puzzled and frustrated....

Attached Images