Had this 2 years ago, some foreigner chancing his luck.
Claimed I had door dinged his car and the claim was £500.
Insurance company's generally do not investigate for such a small some. They usually payout, you lose your no claims and bingo they raise your premium.
Push it till a loss adjuster gets involved, then make sure you have a diary tracking your movements be it work, driving etc.
I won my case but the loss adjuster said it was only my living by my diary which was acceptable as evidence.