Thanks all for the replies, one of your suppliers quoted above or Autoglass seems a good 1st step:
"...Good news is that it’s unlikely to be a bonded screen in that age of car, so easy enough to remove and replace if the rubber seal is in good condition.
The Autoglass web-site has an on-line request a quote section (or a number to phone them) to get a price for a replacement."
I've yet to take delivery, but planning to blog on here as it (probably gradually) gets back on the road!
Iain