Thanks to a kit of [new rollers](http://www.daytonaplc.co.uk/products/HP%20Paper%20Feed%20Repair%20Kits.asp) from [Daytona plc](http://www.daytonaplc.co.uk/) and detailed service manual from HP for my Laserjet 5M, it’s now printing without jams again!
Should last another 100k pages now I hope
(Note to self for next time – replace the upper feed roller before the lower one as the sprockets will be easier to engage with the drive belt that way around.)