IMO - your in the wrong for being in the left lane and wanting to go on and hes in the wrong for cutting into your lane.
But your exit was blocked so you had to go on so you didint have a choice.
if it did go to court, i would just saying i was getting off at the exit and that way, it will be his fault for cutting into your lane.
But - you say he hit your rear wheel arch. I think he was slowly moving in behind to get into the left lane and as he was expected you to get off at the junction, he hit the side when you decided to carry on to the next junction and you cut across him...
What a load of rubbish & my reason for taking a strong stance is purely cause I'm fedup with people that do this, its caused me untold times to pull up & almost hit people & as said they usually give you abuse or the finger, really fecking winds me up.
The guy wasnt wrong to cut in as you say(take his exit), it was his right to move across to the left, the other driver was using the road law & that is indisputable & shaw's exit wasnt blocked at all, he was taking the 3rd exit & was clearly in the wrong lane & there is no way if you analyse the situation that he can goto court & say I was taking that exit & get away with it.
1st he cant say I came of the 1st turning which was the gates exit which would then make him legally ok to take the 3rd exit, he came onto the roundabout the turning before this so he should of been in the right lane in front of this driver & the witnesses would say he was coming onto the roundabout from that turning anyway so which ever way he goes he cant win by road law anyway, pure luck maybe.
But I've been in a legal claim & the lawyer made the other party look so unbelievably stupid & tbh very embarassing for them given they were obviously lying, going along the lines of can you see round corners sir even though you were 5 metres inside a pub with no side windows & the pubs sat back from the road anyway, xray vision perhaps, lol.
Stop looking for excuses & just take a look in the mirror, it was your fault simple as that, you've admitted you were in the wrong lane & take the hit if it happens, it doesnt matter what we say anyway we can make you feel better about it now but when the penny drops & its claimed in the other drivers favour what are these words supporting you going to mean, sod all, follow the road law then you know whose at fault then anything that turns out better than that is a bonus & have to say stroke of luck.
On another note, most witnesses will support you fully at the scene but when asked to give a truthful statement it usually differs somewhat from what they originally saw, interms of they've had time to think again what they really saw truthfully.