I have a discovery 2 tdi5, one of my rear air bags has gone, got some replacement bags, pulled my old bag off on O/S, the fitting on top for the air is not a push fit I had to un screw, are there two sorts of air bag for the td5

The later aftermarket types are "push-fit". There's no problem, just cut the screw fittings off with a sharp knife or a tube cutter. Keep the cut square to the end and do not crush the pipe end such as in the jaws of pliers. Do not damage the end and make sure that the ends are absolutely clean and free from scratches.
To assemble, just push the pipe fully home into the little hole, once they're under pressure they will seal properly.
Always replace the air bags as a pair

Brilliant thank you I was about to buy some more