Am I about to be scammed?

I run an emergency tyre business, and have just had a job cancelled on me. We took full payment in advance by bank transfer (we're in the UK) and our policy is that if the fitter has left we can no longer refund the callout fee, just the tyre.

The odd thing about this one is that the fitter was literally 10 mins away from the customer when they cancelled, and seemed very unfazed when I told them they wouldn't be getting their £200 callout fee back (it's midnight here hence the price!). I asked multiple times if they were sure and even outright asked why they were ok with losing the £200, and didn't really get much of a response.

They have asked me to refund the tyre which I of course am happy to do but their considerable disregard for the large amount of money to be lost has me concerned. I have told them that I can't issue the refund until the morning to buy myself time, and again they were very chill about it all.

I've read on here before about clawbacks etc and sending people money asking for it to be returned to them 'but keep some for your trouble scams' (sorry, I forget the name) so am worried that eventually we will lose not only the full amount paid by the customer but also the money sent as a refund.

Am I stressing over nothing or am I right to be concerned? We have had scams and issues with non payments in the past and have taken many steps to prevent this but the scammers are always evolving!