I had a long winded thread going on this very subject....two starters, battery, alternator regulator, brushpack, starter motor bush, earth leads at gearbox nose AND battery later.... and the propblem would go away, then return.... it was incredibly annoying to say the least. After advice from many, I finally found it was the long run of ignition wire that leads from the fuse box to the starter....simply suffering from its age, and electrical resistance issues. I fitted an ignition relay in the engine bay, and boy, what a difference! No issues since that day!
So... if you have any further problems... save yourself some time and effort and try a £5 relay !
