Halfords sell the release keys you need, ask them for the U bend type keys that fords/vauxhall need to release them. If its a Mk2 punto you will also need a facia adaptor which the above firm sell. If not them you dont require it, if you cant be asked with going there look for 4 small thin nails and you will notice 2 holes either side of the unit making 4 in total, put each nail down the hole and pull via the cassette hole and it should come out.
Rich, January 2005