Just an update on this. Took a bit more than half an hour
but that was mainly due to difficulties getting the bolts out.
First problem I had was getting the bolts out so I could remove the pulley from the PAS pump. Working on my own I couldn't get enough leverage on the crowbar to hold the pulley still so I ended up making a tool to lock the pulley from a large Jubilee clip and a section of Dexion shelving bracket that I'd cut and bent so that it fit across the pulley and engaged against the engine block.
I don't think the bolts had been touched since the old girl rolled out of the factory 17 years ago. A couple of them came out OK but the others the 10mm socket just slid off. I had to hammer on a 3/8" socket and use that to break the lock. Similar trouble with the four bolts holding the mounting bracket to the engine block and the three bolts holding the pump to the bracket.
Eventually I had it off and disconnected the hoses, having first placed a bucket beneath to catch the fluid. Reassembly, as the Haynes 'Book of Lies' regularly assures us, is the reverse of disassembly.
In fact it all went back together very smoothly, with the only glitch being when I realised I'd fitted the bracket to the pump the wrong way round. Bleeding the system seemed to go well enough even though I was still working alone, dashing from the cab to the bleed screw to the fluid reservoir to keep it topped up.
Took the old girl for a short spin and checked the fluid reservoir. It just needed a top-up, and no bubbles
Only other problem was that somehow I'd managed to pinhole the radiator - probably when knocking the 3/8" socket onto the siezed bolts - but a bottle of Radweld seems to have sorted that out.
Thanks for all the help and suggestions, folks. Something else I now know how to do