Thank you MH. I did as you suggested and effected the repair.
If anyone else has this problem, this is procedure i used:-
1 Removed the cover, two screws each side + three at back, this reveals a black plastic cover over the drive unit.
2 Remove four small screws and extract plastic cover.
3 The metal cover of the loading tray is revealed, this is held in place by two black spring clips located on either side near the back of the unit. By pressing these clips inward, the plate is released.
4 The disc can now be removed
5 Re-assemble in reverse order, taking care not to drop the screws!
I McDonagh, January 2008