Apologies, should have said at the start that I am in the UK.
I will post a couple more pictures later of front and rear clearance and in the meantime answer some of the questions raised.
Re drilling for front brake, yes it could originally have been intended for track and then drilled later, but looking at the frame angles, it didn't, to me at least, seem right and hence path/road came to mind. Could be wrong though.
UK had many many frame builders and agree they don't all feature on the classic lightweights site, but I have been through all the pictures on there and nothing that matches up frame number location i.e. on left hand rear dropout and style. There are no visible signs of a head badge and that, and the, relatively, low number i.e. 4 digits, suggests a low volume frame builder. In a small cycle shop they wouldn't be churning the frames out like the bigger boys.
As keen eyes have seen, the Nervex lugs have been worked on, as have the rear stays, so someone has put their own mark on it.
Stack height, I was told, should be around 34 to 38mm and have gone for 34mm and will use spacers as necessary and/or front brake hanger if I go for a centre pull brake. I don't intend to use a rear brake and will keep it fixed.
Hopefully that's all the questions answered for now, but let me know if not or if anything else comes to mind.