Well done
I was always convinced the plastic pulley had broken...as Welly said.
Whilst you are waiting, have another look at the fan belt tensioner, looking at the picture again, there may be another allen bolt above where the water pump pulley is, have look to see if there are any other bolts holding the tensioner on....I was assuming your belt tensioner was spring loaded, hence the reference to a pivot...but it may just be bolted to the engine and movable manually by turning the big allen bolt....it's hard to tell, it's a long time since I did anything like that type.
Make sure you put some silicon sealer on the new pump gasket/seal.
When you fill the cooling system, look for any type of plug screwed into the cylinder head that you can easily remove (temp sender or something), this will help you fill up the system and have minimum bleeding, turn the heater to hot as well.
Tomorrow I have to take my son for a job interview in Preston and in the afternoon I have a driving school car with a brake noise to look at.
Good luck
