need help on this please

sher you have to confront anyway; they might have chnages number, lost yours, showed up and you not there, etc etc.

I would confront face to face and open with “I see you collected the wheels anyway, need to close out the payment so”

In grand scheme it’s only 350 quid so make sure your response (and stress level is commensurate with the loss).

Or perhaps the guards are looking for an excuse to do nothing or pass the buck. Wouldn't be the first time in fairness.

I would say this is theft.

In general, you don't secure ownership of something by payinga deposit on it; all you secure is the right to complete the purcahse of it at a later date, but ownership doesn't pass until you complete the purchase.

So I would report this to the guards as theft.

Having said that, if the wheels were taken by the people who paid the deposit, they can easily make it look like a dispute over ownership rather than a theft by, e.g., claiming that they paid the full amount, or that they tried but the OP refused, and refused to return their deposit, or some such story. And once they do say something like that the guards will likely say that this is a civil matter. Or, they will simply deny that the wheels they have came from the OP, in which case the guards will view this as a claim by the OP that he owns those wheels — again, a civil matter.

Still, worth reporting, if only because the guards will mount some sort of investigation, which might throw up some evidence that the OP hasn't found — if nothing else,evidence confirming that the people who he thinks took the wheels did in fact take them.