I've recently acquired a 1966 Mark X and am in the process of stripping it down before the body work can be done. Has anyone got the secret of how to remove the screw holding the rear of the front seat frame from the floor mount? Even after moving the chair all the way forward exposing the screw, there seems to be no way to actually access the screw as there is no space for a screwdriver. Is it necessary to take the entire frame apart first?

 

Shouldn't be. Basically, one moves the seat forward to expose the rear screws, undo those, then move seat back to expose the front nuts and undo those. (or vice versa). Of course this is Jaguar so you might need a specially modified screwdriver, as they never made things easy for us poor mechanics. Your pics show the seat sliders are very similar to those on my Mark 2 I had in the 80s. I didn't have any trouble with these as I recall.

Actually, thinking about it, you might need to take off the two trim pieces at the rear corners.

 

Fraser is right. Just get under car and spray lube on captured nuts, so they do not spin and break welds then pull seat fwd undo screw and push seat back and undo front.