Right, conclusions from Stretton:
The front end is too soft, resulting in the springs both taking a set, and coil binding under cornering.Cure, change to 30mm diameter springs, and cut them 1 inch longer than neded. Hopefully the pre load will negate any set they may take in use, I can always shorten them if needs be.
The steering was binding, wheel is off centre, and bearings too long. So I'll realign the shaft, counterbore the bottom bearing to reduce the bearing width to about 10mm, and use a conecut from the back of the top bearing to achive the same result.
The pedals are too far back. Now that I can see the geometry I can move them further apart to miss the pitman, and extend them horizontally to move them forward, without obstructing the steering.
Not enough lock. Having freed off the steering, the avaiable lock has increased quite a bit, if it's still not enough I've got two holes in the steering arms closer to the slider.
So all I need to do when I get home is find a bit of privately owned tarmac I can use for testing.