Well , I didn't believe I would learn so much!
Thanks to Western for those links to the retroanaconda site with the parts lists etc; I hadn't seen that before and it's great. I've taken off the fan and fan shroud to get better access and am now driving around without them. (It would be interesting to know what sort of ambient temperatures a 200Tdi will run in without needing the fan!)
LandyManLuke's suggestion of using the 6-sided socket is the next thing I am going to try, once I have got hold of some spare bolts in case of breakages.
ajh's info about the Irwin bolt extractors got me straight onto their site and I have ordered a set from tools247 on Amazon.co.uk for a pretty good price I think, and postage at a fair rate.
I have ordered the two belts from Paddock Spares but they are unable to supply replacement mounting bolts. I am a bit out in the sticks here and I need to find a motor factor somewhere who has something similar.
So until I have the bits and pieces together I am holding off trying again. BUT I am out of the despair I was in and confident about getting the job done, thanks to all of you for your advice. I will be back to tell you all how I get on. Cheers.