Need some help proving im not at fault.

Hey guys, new here but been lurking awhile.
I had my first collision today in 5 years driving I do 10k miles on my motorbike and 5k in the car annually., i know it would at first seem i am at fault - However the other driver didnt see me nor acknowledge i was there until he'd ploughed into my car.

I have a witness statement saying i was already on the roundabout when this car came into me - the random guy was just coming out of the bookies and saw it all, he was adamant it shouldn't be my fault.

I was appraoching a mini roud-a-bout heading straight across. I had looked both ways as this roundabout is notorious for crashes.

I entered onto the roundabout being clear to my right, however upon entering the roundabout a car comes speeding down a 20mph street on my right and doesn't go around the roundabout but over it hitting me.

Prior to him hitting me I had braked and emergency stopped before we had collided but he hadn't noticed i was there or he wanted to crash for cash. Either way he hit into my drivers side bumper with his off-side bumper but because he didn't brake he carried on for a more inches until he stopped.

Now i am worried because technically he has right of way but he wasn't on the roundabout before i set off, he was going well over the speed limit and had not followed the roundabout, if he had he would of seen me approaching.

My car has no damage other than a few scratches where his car hit mine however his whole front end is dented in.
I don't fancy being liable for this or a 50/50 claim. What are my chances?


Pictures wont work, anyone know how i can upload some?