well, here's an update, if anyone is interested.
after much trial and error I narrowed the issue down to a loose connection in one of the many wires that enter this grey square box (which is the gear selector box) , and this was causing the car to think it's in 'drive' mode, and hence refusing to start (even when gearstick in is 'park' mode)
photos.app.goo.gl
these wires go down into an this area (see arrow in pic)
photos.app.goo.gl
..here they enter a 90 degree turn and go to the right.
i couldn't figure out which exact wire had a break in it (they all looked ok), so i just removed all of the wires from the plastic sheath thing and removed them from the 90 degree turn (ie straightened them out), this seems to have cured the starting issue, for now...
obviously the ideal solution is to replace the whole loom but that's beyond me and i don't want to spend a fortune on a car that's only worth £1,200
thanks all..