Looks like my 50 layout will be 14.2 gauge in 3mm after all.
A couple of things have become apparent –
1) my current stock is 14.2
2) I have acquired a couple of points secondhand which I can use
3) my doing Southern in 14.2 might spur on a certain gentleman to get on with Hawkhurst and I can run my stock on it
4) I have not gone to far down the line in that I can still do this
5) I picked up some finescale Terrier size wheels which I can get that nice Mr. Shirley to SQ for me
So there you go. Comments and ridicule welcome.
I even have a name for the layout – Martins Road.