I managed to remove the pulley wheel very easily with a borrowed pulley puller and plenty of plus gas . it simply popped off . Such a relief ! I was then faced with the unenviable task of removing the water pump body attached by heavily corroded and rounded ( not by me ) bolts. I used a newly purchased set of Irwin Bolt ‘twisters’ which to my astonishment bit into what was left of the bolt head after a few gentle taps . Initially they bit and felt that they would snap and I had accepted this might happen and was ready to drill out and tap etc. but suddenly the bolt moved and within ten minutes the pump was off. There was some corrosion where one of the bolts fastens to the aluminium casing but I will use a special sacrificial compound whose name Ive forgotten with the new stainless steel bolts.  New replacement pump , new bolts , no more maintenance /  access problems on water pump. !!