I've been looking for a cheap Mac compatible gamepad and found this one.
It's at the AppleStore for £24.95, though the RRP is £19.99! Comet is currently selling it online and in-store for £14.99, £5 off (though their website says £4).
Picked up one today after reserving online. Standard delivery is a whopping £5.95 so any free delivery vouchers would be welcomed.
I'm sure there are better gamepads out there but for us Mac users the choice is far more limited.
Hope this is of use to someone else facing the same predicament.
Thanks to everyone who has posted. If you spot a bargain - post it and hopefully it will be of interest to someone else too.
All the best!