Hello Bob, many thanks for your reply. Right enough, I reckon its worth changing the bearing.
I emailed Listers about spares, and they passed it on to Sleeman & Hawken Ltd, from Teighmouth, Devon. They emailed me yesterday & said they held AC1 spares, and are Lister/Petter's UK parts agent. I've enquired about Oil, Air & Fuel filters, and also asked them if they hold Markon spares. I'll let folk ken as soon as I hear back.
Regards, David