Well the radio was fine, just a blown fuse. The strange thing is not that it was blown but that it lasted so long through three VHF's.
The fuse was only a 3A one which rather surprisingly objected to more than 5A going through it when transmitting.
This same fuse has been operating the VHF for 18 months now without complaint even though all the radios fitted have drawn more than 5A transmitting.
In saying that fuses can be unpredictable, I remember one guy plugging in a faulty table lamp with a 3A fuse in it and it blew the 250A pillar fuse outside the building, bypassing around 4 fuses of larger and larger capacity till it got there.
I'll go away and be embarressed now