Thanks for all your comments. It’s been very reassuring to read them.
As people have said this type of event is very rare – I am in my mid-fifties and this is the first time something like this has happened.
I did report the incident on the same day by email to the manager of Glyncorrwg bike centre. As I haven’t yet had a response to that I decided to join this forum just to make this post – which is why my first post is rather negative – sorry about that.
I considered reporting to the police, but I have few useful details (four male mountian bikers, probably mid twenties, one called Chris) and to be fair to them I feel sure that once they calmed down they would have realised that their behaviour was over the top. In fact of the four one was quiet the whole time, another two mostly just shouted at me, while it was the last who had a severe anger management problem who did the spitting, pushing and almost continuous strong verbal abuse with threatened violence.
It was unfortunate that to walk away I had to walk past them (within spitting distance) as the bike track was behind me and they were across the footpath ahead.
That one rider probably needs anger management therapy more than police intervention, but his friends should have been aware of his nature and tried to calm him rather than join in his shouting.
Anyway, I really appreciate all your comments and feel much better after having shared this here (as I’m retired and live alone). Hopefully I’ll be able to get a good nights sleep again now.