The AA are offering a £20 Boots voucher when you take out cover on recurring annual payment. Not available for existing customers.
Only available over the phone, call 0800 2947812 and quote ref 1005.
Personally I think Autoaid is far better than theAA, but if you want a year's basic cover for £15 then this ain't bad. You can always cancel the direct debit after the first payment has been made.