Hi Tony
This looks to be a good project, there are a surprising number of these B-L engines that turn up part finished or needing restoration, in fact there are lots of 2 1/2" gauge part finished's around, presumably started in the earlier years of the hobby, and abandoned when the larger gauges became more popular.
I'm rebuilding a part finished 2 1/2" gauge loco at present, and posted on here under " another president causing problems" , I can't help with the rebuild I'm afraid, but I have done some work on one of these in the past for a friend, so quite happy to give any advice i can if you PM me. Best recommendation I can give is to join the 2 1/2" gauge association, theres a wealth of knowledge and they are a friendly helpful bunch.
I think part of the criticism of the design comes about because they were not designed as passenger haulers, and were derided by model loco designer LBSC because of this,at the time he was building coal fired more powerful engines, but these make up into very good looking models with the right look.
The engine looks fairly complete and appears well built, if you do restore it yourself, take copious notes and photographs as you dismantle it, I put everything in such as screws and tiny parts in small envelopes and label them. Working on small sections at a time, say front bogie, or cylinders as assemblies helps to keep the work orderly. I have seen loco's where everything has been dismantled and chucked in a box, by the well intentioned restorer, tragically it found its way to the dustbin next. Good luck with it, it is a very worthwhile project.
Dave