I had a painful time for a while trying to get a certificate of conformity for mine. Land Rover wouldnt issue one due to it being 'MOD spec' but they did give a build date. In the end it was just hitting the 10 year old mark and I didnt need it.
I found varying levels of help from different DVLA offices, Oxford were better than Reading for example.
I think youll need all the usual build date, weights, body type etc..
Cheers
Colt