Sounds v.similiar to mine last year. Only mine was on a bigger scale.

I had 2 witnesses and for some reason his only witness lied like fuck and he didn't know the guy. Anyway out of the 3 witnesses we had 1 each supporting our story of events and one sat on the fence! I accepted 50/50 and lost some of my NCB. If i'd contested and it had gone to court as the tp wanted it would have had the same end result but put both of us to the bother of dragging it on.

You shouldn't lose yours if the witnesses support your story. You'll just have to recover your excess if its non fault through the ulr legal peeps. On mine the damage cost less than the excess so i didn't even submit a claim in my part £470 i'll not see again.