Following the advice of the knowledgeable decided to check and clean the scuttle area, had a right game with the windscreen wiper arms which were well seized onto the spindles. I had to modify a puller to fit the drivers one and apply some heat with a pencil butane torch fitted with a catalyst tip so just hot air and it only just let go. The scuttle area thankfully was quite clean. When cleaning the plastic cover I noticed some plugged drain holes in the wiper recesses, while not being able to let the spindles sit in water I feel being sat repeatedly just above this small amount of water while it evaporated probably for years certainly didn't help matters. Wiper arms refitted after a thorough cleaning of spindle and arms and with a generous coating of anti sieze so I'll see if it's any better next time.
Regards Chris

Drain holes