3.0 CSi's procedure is correct. There are two L shaped brackets that are welded to the body (one for each seat) that 'interlocks' with a slot on the back of the fibreglass seat frame. This is the only device that is holding each seat in place. Grasp the seat bottom, lift up slightly and push down from top of seat back. This will disengage the seat from the body bracket, do this gently as you don't want to break the brittle seat back fibreglass.
When refitting the seats, make sure you insert the seat back slots into the body brackets. Make sure you do this as you the seats will look seated even without the 'interlocks'. Pull from top of seat, if it is installed properly, seat will not pull out. If not, during a emergency panic braking, the whole rear seats with it's contents or passengers can be thrown forward dangerously.
Bert
72 3.5 CSi
88 M6