Thanks for the comments guys.
I'm not in work this Friday so I might pop down to my local Police station then, if I still feel inclined that is. Will let you know how I get on.
Regarding the reg, from looking at the raw footage and pausing as he goes past the reg does indeed look like FE31XJA. However this is obviously nonsense and I do read out the reg nearer the roundabout on the video as F531XJA. It is the second digit that is in doubt, and both registrations seem odd. I'll check the raw footage again tonight frame by frame.
Regarding HGV drivers in general. I actually have a high regard for their driving and have commented in conversation in the past that I think HGV drivers and traffic Police (definitely not referring to your average plod here driving their 'jam sandwich') are some of the best drivers on the road. And I think in general there is an element of truth in that statement, in my experience anyway.
I think BADGER.BRAD is correct and that the driver didn't want to have to change down his gears. I can understand that, but to place a vulnerable road user in so much danger like that just isn't on. I'm sure you'd all agree, the most important thing to consider when driving / riding is safety - safety trumps all other considerations. That didn't happen in this case.