Maybe worth trying to find out the pin assignments for the socket? Quite likely two of the pins are connected directly to the microphone and two for the pressel switch, and any basic hand mic could be substituted. RS almost certainly sell a plug that will mate with the socket.
For the effort and costs required to try to get it working..........not knowing even if the radio its-self even functions.......... I would be thinking it could be time for an upgrade???
You could try speaking to your local marine electronics dealer and see if he has any lying around, if he does he may even test the radio for you. Lots of people have upgraded to DSC vhf radios and there are a lotof the old vhf's around.
Finally got to have another look at it last night and unfortunately it has an 8 pin, din socket on the front which is a) different from the 4 pin one depicted in the manual that Aardee kindly found for me and b) makes it harder to guess.
Think I'm coming to the conclusion that you all came to within 30 sec's.... its time for an upgrade :-(
Also came across some information regarding change of manufacturer - pins same though changed for multi pin plug and socket - open yours up and check the wiring at the back of the socket
Thanks, that circuit diagram also shows a 4 pin plug but I'll do what you say and take a look inside. If only 4 of my 8 are used that will at least make the process of trial and error easier