http://www.bikeline.co.uk/ – not sure if they count as ambulance chasers, but they’re experts at this sort of thing and will get what you’re entitled to. Then just follow their advice in terms of quotes for bike, getting medical check up etc.
IME even if the driver admits liability at the scene, as they did in my case, the insurance company may still decide to try and avoid paying up and will have to be threatened with court action. Mine was exactly the same as yours (if I’ve understood correctly), I was on the roundabout and a car entering hit me.
(there are other options who I’m sure are as good, but they’re who I used).