Its hard to say about UK manufacture. As far as I'm aware there are actually more steam locomotives being built in the UK than modern locomotives at the moment! The only Diesel locomotive I can think of that is in production over here is the Hunslet 0-6-0 super shunter, and I'm not sure how many have been sold, but it certainly isn't many.
By 2020 though, I think we'll see a fair few more of those around, as 08s and 09s are becoming more and more difficult to maintain.
A big shame was the sale of Brush Traction to Wabtec. Yes, the Name Brush has been Retained, but sadly Andrew Barclay and Sons (Ownded by Brush) has had it's name eradicated entirely, and the Kilmarnock works is now known as Wabtec Rail Scotland. Hopefully the future will be bright for these two sites, but independant British builders are now looking very thin on the ground.
To be completely honest, privatisation of the nations raiwlays was a huge blow to home manufacturers (there were only a few left even then!), so if there is to be a resurgence, I think it will have to involve the industry rebuilding itself, almost from the ground up.
On the brighter side, Bombardier still operates Derby Carriage works and part of Crewe works, and whilst these places (mostly Derby) focus on the building of multiple units, the company does have success at building locomotives at their Canadian and European factories. I think it would be lovely if some of that experience was brought over here.
Many thanks for your input,
SFE
