It is a closed currency so in theory you shouldn't be able to get any MAD (Marod Dirham) outside of Morocco.
One of our customers on the November 08 trip did, however, manage to exchange £ for Dh at Gatwick on his way out, so it may be worth checking.
In the Menara airport in Marrakech there are several cash machines and two bureax de change- their rates vary a tiny fraction (so small it's not worth bothering about - I change £3000 at a time there and it worked out at about £1 different last time).
There are also cash machines by the dozen around Marrakech and nearly every town has one too.
You can also find some nice machines where you stick in notes of other currencies and get out dirhams...pretty neat but crap exchange rate.
The best rae can be obtained by using some building society debit cards in the cash machines.
The rate is dropping

11.673 to a £ as I type this and you won't actually get that rate in real life- if you think of ten dirhams to a pound you won't be far wrong when looking at prices.
Having said all that, food, fuel and accommodation is still a lot cheaper in Morocco than in the UK or across most of Europe
