DH finally called HMRC to check if he had overpaid in the previous tax year (after much nagging from me). We were pleasantly surprised to receive a letter from them this morning saying not only do they owe us almost £3k from 2015-16 they owe us almost £1k from 2014-15!
It took under 10 minutes to make the call. Go on, it has to be worth a try!