Thinking caps definitely on there! Thanks for the replies. The 4/4 sport has sliding seats and the tracks but up against the suspension mounts so they can't go any further back or so I'm told. Would be interesting to see if a specially made seat with less padding/lower base could be made as that would clearly give me more space. The wheel on the car was already a 14" moto-lita so I can't imagine they get much smaller than that.
I think that a changing the pedals would be a major improvement - maybe getting some CNC machined might be possible. The floor mounting is just nightmarish for adjustment though and makes it really difficult to rest your foot under the pedal when you aren't changing gear.
Thanks for the thoughts and I'll keep updating on any progress.
Andy