Yes - it was working perfectly!

The SIMMs plugged in are 4 x 16MB in Bank A, with 4 x 1MB in Bank B, making 68MB in the only configuration that's known to work (according to the Repair Mac site).

The chimes are pretty much constant now, so I've got a weekend of playing to get it working again. I'm thinking maybe a contact clean with some isopropyl initially, with who-knows-what after that!

Thanks again!