LDB wrote:
Had 2 motorbikes on collarbone

- came absolutely pegging it along there which was outrageous as there were walkers and it is not very wide. Then another 2 on way back on NDW that came flying past and came really close by, its a wide track so it must have been on purpose. Living down to my (exceptionally) low opinion of the scrambler brigade.

Very annoying as neither are Byways open to all traffic.
Unfortunately as in any walk of life, there are always the few idiot's that spoil it for the many and disobey the rules.
Please don't tar all off road motorcyclists with the same Brush Lloyd. I would be angered by the two idiots you encountered. I know many trials motorcyclists ( of which I am one) who abide by the strict country code of the TRF (Trials Rider Fellowship) and they hate those idiots too.
The TRF actually do a lot for the countryside, not just ride on the Byways. Unfortunately you don't have to be a member to ride the byways and the type you are talking of would not commit to being members.
https://www.trf.org.uk worth a look as it explains their ethics and commitment to keeping the byways open for all.
They are the same as us, just wanting to ride their motorbikes off road rather than on road and experience the countryside.