Right, I sorted the arcing contact. It turned out that one of the lower brass nuts on the connector block was loose, even though the top nut was tight, so it was hard to spot the problem. anyway, I cleaned up the connections, retightened everything and fitted the new start cap that arrived same day. Powered it up and it ran perfectly, start after start after start. Bob on. No fuses blowing anymore. And tbh, though maybe it's just my imagination, but the comp seems to start up more positively and quicker.
Anyway, all's well, so it must be the end. Thanks for all your inputs guys, much appreciated.
