Seems to me like a job for Denis Waterman; he could also sing the theme tune.
Serious answer: possibly Ken Stott, if he can get the accent right.
If ever a story was begging to be made into a biopic (done properly that is) it has to be 'The Villain': Climbing, post-war social history, class politics and stunning locations. Properly cast over about a dozen episodes, if anybody still commissions that kind of project.