[Ashlandchris]

Cheers Jim, and everyone for their advice.
I got the front end off last night and it seems that the problem on Friday night was that the 3mm screw holding the post for the servo saver had snapped so I have managed to get the screw out as well as the broken shaft. However, this doesn't get away from the fact that the servo saver is very spongey.
Obviously the tension in the servo saver is controlled by the spring and the whole assembly is held together by the e-clip that clips onto the shaft. I.e, tightening a screw doesn't tighten the saver at all.
I have just tried to add a washer onto the shaft to compress the spring slightly but can't get the e-clip in place with that so...

If I glued the servo saver this will sort the problem, but means my servo is at risk.
I am going to see if I can get the parts for the Lazer ZX as suggested by Alcyon. The shafts seem to be rarer in UK and I'm not sure yet which steering plate it is as there seem to be a few from a cursory search in google.
I'll keep you updated...