Premier Inn Hotels review: Charged me twice and won't refund

We had paid for our stay at the Premier Inn Birmingham in advance but when we arrived at the hotel we were told that no payment was on record so we had to pay for that night - even though we had the booking reference, etc. We paid, thinking we could quickly sort when we got back home. However, that was 8 weeks ago and many emails/letters/phone calls later, we still have not received a refund. Still chasing them!