[user104658]

I'd be wary of "unidentified" HMRC payments though Cherie, call 'em up and ask what the payment is. If it's an error they'll snatch it right back with no questions or protests .

A friend of mine made that error when we were at Uni. He was doing a bit of freelancing, got a random £250 in his account... immediately spent it... only to be hit with a demand for immediate repayment. He borrowed the cash from me and paid it back by "paying for a round" every time we went out... for literally nearly 4 years. Should have charged interest.