Having now completed the task,teh most tedious task I have undertaken since being an apprentice, I can confirm that I did not need to remove the window frame. As guided by rcharman, thanks Australia, just remove the bracket, a real mickey mouse piece of kit and what it's function is I have no idea, unbolt the frame which provides enouigh clearance to get the agricultural window regulator past the frame and out.
It was twisted compared too the previous photo provided, so gentle persuasion via a bench vice and stilsons, soon had the arm in alignment, well near enough as this is hardly precision engineering!
Reinstatement is even more boring, watching paint dry more exciting.
I now remember why I had Ford's in the 60's rather than BMC.
Still, thanks everbody for the help, I just need to find a surgeon good at skin grafting! Any suggestions?
