Yeah, that's what I guessed. Why was the filter lane unavailable?
I'm guessing that he misjudged your speed and expected you to be going quicker than you were when you let the other car merge ahead of you, so when he turned in he expected you to go. Or you may have slowed up unnecessarily, I don't know. Clearly his fault for running into you regardless, however that's tough to prove. He may say you swung out, or anything else that puts him in the right and you in the wrong. Regardless, it's not something I'd remotely worry about right now, you need to get further down the line and see what they say.
Why would you have to get rid of the car if you lose your NCB? There'll always be an insurer willing to take you on for less, and given that you'll have to pay your excess anyway if it goes 50/50 you can simply put that cost against the repair bill of fixing it yourself. There's ways and means round it, just remember you're the customer and you can take your time deciding what to do. Feel free to PM me if you want to chat further, or if/when things progress a bit more and we can chat through your options in more detail. Don't panic my friend, we'll sort this out in your favour somehow, promise.