Thanks kink for that info...
I actually managed to fix this today i pulled the drivers seat out and had a look underneath there was a bolt missing god knows how...i dont think it could just fall out.
I replaced the bolt using one from my old seat and it fixed the issue thankfully.
I now wish i had checked my old mb3 4 yrs ago to see if it was this bolt missing or something else.....cant be bolts missing on all those affected as you say it would be weird.
Have a look soon and post back here what you find..
Actually...i just had a thought, it could be the bolts (theres 2) are loose and need to be tightened up??
Worth having a look as this can be really annoying as in my case.