MY daughters mini one passenger seat has a wobbly seat back. I have difficulty locking it on to the ratchet, and when it is locked on there is about an inch of movement back and forth. Can anyone help?

Might be the actual seat steel frame thats fractured or partly fractured, early cars had this problem, you might have to slip off the seat rear cover to find out for certain.

The seat back appears intact and the whole seat wobbles form the pivot point as if it has not engaged properly on the ratchet mechanism any further help would be appreciated

This link may help you:
Seat Problems & Solutions - Forums (http://forum.minicooper.org/showthread.php?t=12641)