Mortgage taken out 1989 and redeemed 2005. 225 "sealing fee" paid. On request NWHL readily refunded 140. When I wrote to point out that none of the 1989 papers (of which I enclosed copies) mentioned any "sealing" or exit fee at all, they refunded the remaining 85.
So: good for them for acting quickly after both contacts and for eventually paying up in full. But I was not impressed that they tried to claim in effect that I had contracted to pay 85 in 1989 when they knew perfectly well that I hadn't.
Moral: if dissatisfied with level of refund, don't give up.