Hey Philp-
A couple British Chinooks were stationed at the same place i was in Saudi, and if can recall correctly, they did indeed have the overhead door winches installed, along with the mini-guns; although i'm not too sure about what they had on the ramp since i never saw them with their ramp(s) down. I believe they also had the EAPS (Engine Air Particle Separators) installed as well. US Chinooks didn't start installing EAPS until late '92. In fact, my aircraft (85-24347) was the first a/c in Army inventory to have EAPS installed....so that's sort of a cool bragging right.
Not to sure about the rovers. But i can tell you "if" they did carry them inside, they still would of had the aircraft configured with standard seating. However, when Desert Storm began, we removed all of our internal seating on the Chinooks for mission purposes to accommodate more troops, and faster onload/offloads.
The rovers themselves (if carried) would have been secured with 5,000lb cargo-straps, or 5,000lb tie-down chains. These are pretty standard equipment on all Chinooks, and i can't imagine them using anything other than that - except maybe a couple 10,000lb cargo-straps.
Hope that helps a little.