Water pump replacement Daimler v8

I have a new water pump to replace on my V8 250. This is my donor car but I need it running so looking to get away with just new pump and gaskets. Looking at the bolts/nuts I am not sure how to get a spanner in there behind the pulley. Can anyone offer advice or experience to assist please? A six sided ring spanner would be best option but I don’t have such a thing! I know the pulley will be a pig to remove but I have access to a press locally so hope it will come off in one piece.
So I am removing the fan and hoses but not removing the radiator. There is no shroud so I should have room??

Well I managed to remove the pump after all after considerable fiddling. If you don’t know you will need as thin a ring spanners as possible cranked to get the bolts loose but taking the ring spanner too far means you cannot remove it as it will not clear the nut once it is so far up the stud! So once loose use an open ended spanner to mm by mm get the nuts off. Another hour was spent encouraging the pump body to come off the studs. Not a lot of room to swing a rubber mallet but it come off eventually. I then removed the seized tensioner pulley and cleaned it up so it now works. I await my local engineer to remove the old pulley so i can replace the pump. Standing for 15 years does not do water pumps any good.