Took the motor to bits today.
It was quite hard to turn by hand.
Looks good inside. No burn marks, plenty of brush left. Slight blacking on the pick ups which cleaned up nicely.

However, putting it all back together there was a threaded bung that screws into the top of the motor. This was filthy with dirt etc. I screwed this is in then could not turn the motor by hand. The more I unwound the bung the easier the motor turned by hand.

Didn't get a chance to get it back on the car tonight so I'll see if this has made any difference.