Pete, it's great to see such a well researched post here about something which is really useful to others. Rear screen heating isn't the most "sexy" thing on the car - it's a safety feature! - but we've had the discussion a few times now, and it's really good to have a tried, and reasonably good solution to the problem.
If you can, I'd like to see some detail photos of the result, but in any case: congratulations with the repair!
Cheers,
Anders