Unused stamped envelopes - possibility of a refund?

[Simon666]

A few years ago I went to Australia to work and before I left I addressed and stamped 20 C4 envelopes - at £3.60 each. A total of £72.00.
These were for my dad to send-on any mail I got at his address, which was my address before leaving for Australia.

Unfortunately he got alzheimer's disease pretty rapidly and the envelopes were never used.

I found them recently when I was cleaning up his house.

The stamps were the old ones from before the change to the barcode type and, of course, they're useless now.

Is there a way to get refunded for these old, stuck down but unused stamps?

Cheers