[GazYorkshire]

I've experienced this from an admin point of view for a couple of different clubs.
As soon as you start to introduce sections for other models, your original club becomes diluted and loses it's identity.
On the one hand you do have the variety that different models and their owners bring, but on the other you lose that individuality that the club originally started out with.
There are two schools of thought usually - expand the club to include other models and therefore increase the membership, or stay one make one model and keep a hardcore of enthusiasts with their expertise.
Personally, I'd go for the one make one model approach (and yes I know that a Rover isn't an MG, and a 75 isn't a ZT, but that's splitting hairs) and choose quality of membership and exclusivity than quantity of members with a diluted club.