Welcome to TM Joe and good luck with the search for your steed.
The book below has a very comprehensive buyers guide included in the Suffix, some draughted by Phill Benfield of Allon White in Bedfordshire. He was an apprenticed spanner man for them before he moved into their sales area. I think he is a nice guy to deal with although he didn't have the +8 I was looking for at the time.
I found it most useful in looking for the +8, there is also a history and variations in models and running gear guide included.
You will find this book on ebay most of the time.
http://www.motorbase.com/publication/by-id/127821082The GoMog site is a very good knowledge gathering library for most models as well.
http://www.gomog.com/If you have any problems finding it PM me and I'll scan a copy of the Buyers Guide over the pond to you.
Regards
Richard