I removed the insulation tape and cleaned the inside of the rim with meths. The inside walls of the rim were slightly sticky and there were one or two areas which were rough (a bit like light filing marks.). I then fitted the new rim tape which was about 2mm narrower than the insulation tape. I ended up using some window cleaner to help seat the tyre, and it looks pretty good now.
I need to try the same with the rear wheel.
I really just want to try the bike for now. If all goes well I'll probably splash out on new wheels with slightly wider rims.
The valve\pump is still not working properly. I had tried pushing the valve core in to release some air, but that didn't help. I suspect the pump head might be worn. It's an old Blackburn Airtower Shop pump which was expensive at the time, but I'm not sure Blackburn are still in business, and I'm not sure the pump head is still available as a spare part, so I may have to buy yet another pump!