Hello Manfred,
Lots of information on British jazz of that era on this site, including Westbrook, Gibbs, Collier and co. Just do a search using some of those names and - voila !
May I recommend the book ‘Music Outside’ by Ian Carr, reprinted by Northway Press, as a very good overview of that period of ‘British Contemporary Jazz’, superbly written by Mr Carr as an insider’s view.
in terms of recent releases/finds, I recommend having a look at the ‘Jazz In Britain’ Bandcamp site to sample big band material by Alan Cohen, Neil Ardley and Ray Russell’s Rock Workshop. Also check out the Alan Wakeman Octet release on Gearbox.