Well, I'm glad you all have your thinking caps on! Thank you for all the suggestions so far. You could well be right about freelance- the spectacles are stumping me but I have a feeling I have seen similar ones somewhere where round ones interfered with a later Belpaire firebox and got modified- I think L&YR did something similar but only on tender engines that I am aware of. I initially thought it might have been a L&YR loco later in life but not so sure now. I suspect later in life a lot of engines received Belpaire fireboxes on rebuild but not necessarily well documented.
Matt, it is very similar to photo 2 on the Watford and limerick. There were very similar locos here in Melbourne that started life as 2-4-2's and became 0-6-2's later in life. I think both Vulcan and Beyer Peacock churned very similar ones out.
The chimney is a red herring, it's a Walsall one I have fitted- the original one was awful and badly made- looked like a cotton reel.
The colour is dark green, no other markings or number. The front coupling is a very weird arrangement- has anyone seen anything like that? It adds a certain Colonel Stephens dodginess to it.
The setup is three rail with a Bassett-Lowke spoon pickup.
The motor runs or ran when I last tested it, no leading or trailing wheels and horn guides etc all somewhat bent etc. Likewise the loco had been dropped at some point but I have now straightened that damage.
I was hoping the backhead might give some clues.
Any other ideas? I am trying to get to a point where I can fix or remake remaining boiler fittings, spring hangers etc and decide on a livery. The final aim is to push and pull around various Carette and Bing for B-L coaches and wagons now that I have a small length of B-L track- literally the Gauge 1 version of 40057's wooden sleepered track.