Cheers Mickeyw.
I don't have a centre seat so the three point idea isn't really the road i'd like to go down.
The idea would be to safely fix an isofix seat base so it sat on the tunnel cover, making it a few inches lower than if it was sat on a centre seat and hopefully so that it'd be still possible to change gears with a rear facing baby seat, then when the brat gets older buying a forward facing seat that fits into the same base.
In theory I could fit some square u bolts with spreader plates through the rear bulkhead so the base would clip onto them, but i'd prefer something a little more over engineered.
Any more ideas are welcome.
Ta, Matthew74.