For everyone's information, Alex has been as good as his reputation would suggest, and offered a free number one clamp and resi-neck. Considering that the problem seems well to have occurred because the alloy insert was not as far into the pole tube as it could have been, this is pretty good service, is it not?
For anyone who's interested, I've decided to dump the quick release version and buy another soft brush, as the stiff one I found somewhat agressive on sashes and postage stamps. My error was in buying one SLX with a fixed head and one with the quick release mechanism. That was not such a bright thing to do. With this outcome, I can rest assured that the end of the pole is stronger and it does away with the pole hose being crushed by the thread on the angle adapter.
Hope this helps, and thanks to Alex and Sam for their help.
Tim
ps, the stiff brush will be eBayed in due course for anyone who needs one.