Thanks for the advice, I was unsure if a key slipped down the side of the
unit or, as is the case, into the four holes.

Pushing four nails or similar items into the four holes, then sticking
your
hand in the tape player and giving it a good yank also works

This will be my first angle of attack!!

Google is your friend.

Google is indeed my friend .. but a bit of a two faced friend who keeps
changing his mind on what way to go ;-)
Seriously, I checked google but found conflicting instructions. I thought
(correctly) that I would get better advice here.

All the best

Tim