Irrespective of springs, even if they were cream cracked with the rear end sat on the bump stops the shocks should not be fully closed. The rear of the car would be much lower than the front and look wrong if there was a spring problem supporting the car.
I suspect if the car sits right that after market dampers of the wrong closed length are fitted.

Your dampers should be either MGB lever arm dampers or MGB after market dampers.
The only alternative is that you have a Marina based car or perahps even a Ford based car - very rare.
I suggest that you send picture to office@ngcars.co.uk of both the car and the rear spring and dampers. I am may be able to help more from there.
Nigel Brooks
Findhorn Cars