In reply to Ned Eastwood:
There are some little companies like https://madebyscavenger.com/ that upcycles a lot of climbing gear. Not sure about helmets but certainly harnesses and other soft good. They've seem to have a good imagination so i;m sure they could take most if not all off your hands. They also have drop off points around the uk so should be fairly easy to offload it all.
There are other companies as well, have a google around...
Other than that local scout groups will probably be happy with shoes etc if usuable
Post edited at 11:14