Well, after consulting my local luthier at Rock Repairs I took Tony's (VH2850) suggestion/advice and got a replacement Switchcraft socket. Actually I got 2, the one Tony linked and another that is Black and I thought would fit. Which ever I use forces the other into my ever growing spares box...
The Black one is the best fit yet it's still a little too snug on the lip for my liking, but it fits better than any other option. To be honest it is the only one that will fit in the hole. I suspect there could be some touch up repairs to the finish in the hole after I fit the socket at the wiring stage.
Another just discovered aspect is there is no way of putting the nut on the socket once it is in. The socket may be some 40mm long but the hole is close to 55mm deep, so some serious mining is needed in the control cavity to expose some socket thread so I can put a nut on it... Don't want to be trying to pull the lead to the amp out and have the whole socket and internal wiring of the guitar come out with it....