where can I exchange Maldavian currency back to sterling in London?

Answer 1

Actually, you might want to consider selling it as a collectible if it is in decent condition. Depending on which denominations, dates, and conditions you have, I might even be interested myself (paying 90% of the rate on www.xe.com)

Answer 2

Check the Post Office. If they say it's a prohibited currency, you're out of luck. In that case, give it to someone who you know is going there, so it ain't wasted.

Answer 3

Use it as a toilet paper,that's it's only use outside Maldives.