Thank you for your comments. In the UK, Hyperbaric Therapy is little known or understood - except by those directly involved. I had a word with the guys running what I think is the only major decompression chamber in England, if not the UK. They were very positive about the benefits. But not happy about the ignorance of the therapeutic implications. The London Chamber has closed. I have arranged to go to a small local chamber that only goes down to 10m. It is used primarily for MS and is run as a charity. It may not be deep enough - in which case I will have to drive for 3 hours to get to the big chamber. It will be a matter of trying to measure/assess how effective the treatment is, and how long it lasts.
Diving, even in the local pool, helps, but symptoms come back after about a week. If I'm down the pool every Saturday, so be it.
Will post again if I come to any conclusions - it may be helpful to others with concussion and/or stroke.