Thanks for the info. Having spent a few minutes looking at the Internet with your info I find there is a net address for that company which is "www.lister-petter.co.uk". Note the hyphen in the middle, most important!!!!
Most parts very cheap - I use a devon based company - Sleeman & Hawken of Shaldon, Teignmouth who are very knowledgeable. The engines aren't limited to marine - they also feature in dumper trucks, so the marine engineer who I use is co-incidentally also a plant engineer!