Hi John, and another
It used to be reasonably easy to get background on our cars in the UK because if you asked the DVLA they'd send you details of previous ownership, log book details they had, etc. This was only for "historic vehicles" so you had to tick the boxes, pay a nominal fee (£5 ?) and I got an A4 envelope in the post with xeroxed pages which included the supplying dealer from new and changes of ownership.
They might still do it but I do remember some discussion about people having trouble and being refused the service a few years ago. Always worth asking, they can only say "no" can't they ?
I think your main source is Andy Graham, the Lotus Archivist, (AGraham@lotuscars.com) who is/was collecting chassis plate details for his records. There's a post on here about when he started
http://www.lotuseuropa.org/LotusForum/index.php?topic=1545.0We swapped emails on my car a while ago but I know he issues "Certificates of Provenance" which includes what details Lotus have of your car when first sold. There's a fee these days but I've no idea how much.
The only other places I can suggest are Club Lotus and The Lotus Drivers Club. Although CL seems geared towards the modern generations in the 70s/80s it was very much an Elan/Europa club and someone might pick up on the distinctive number plate. The LDC is/was very enthusiast based so again someone might pick up on the number.
Cheers
Brian