Suzuki Club UK

I put it on the rear door in the end, I was too scared to cut into the actual bodywork

I have just bought a mag mount for my cb,not really sure what size aerial that i would require ??

The mag mount will of course mount on the roof of the Vitara,the reason i went for a mag mount is so that i can take it off when not being used as it could get nicked,they had 2 reasonable aerial's one about 30'' long and the other i guess about 60'' of course the longer one would get out further distance,but as most of the time it would be close distance i am thinking the smaller one could suit me for what i need.

Any help would be most welcome.

Personally Im a fan of the firestik antennas.... Good brand, been about for years
For best reception you should ideally mount the aerial with the coil above the roof line, although its not always possible!
Basically though, the longer the better. Ive got a big whip antenna on mine, and although its mounted quite low down it sticks up about a foot over the top of the roof. On an off roader I'd rather as long an antenna on as possible, then you can mount it low down and where it is springy it doesn't matter about bashing the top of it into trees and other overhead obstacles. I do lose some signal strength from where it is mounted, but IMHO its worth it to keep the mounts well out of harms way.
If you're using a mag mount thought it will have to be a short aerial anyway. The problem with a mag mount is, because the have a ground counterpoise as part of the cable, instead of using the vehicle as the ground plane, you will usually get 15-20% less signal strength compared to the same aerial mounted to the vehicle.
I would avoid using gutter mounts on an off roader, as they tend to bend the roof gutter if they get caught.