I would suggest looking in the ANO (CAP 393 from the CAA web-site) as a first step - specifically Section 1: Schedule 4: Aircraft Equipment. This will indicate the minimum equipment required for various types of aircraft / flight.
The you want to check with your engineer / inspector - as he is the one who will sign it off. (No point in being able to say "but it says here" if he isn't going to sign the chit).
OC619