In today's Metro paper on the 'Guilty Secrets' page there is a voucher to get a "free bacon butty when you buy any medium drink" I asked what drink and he said anything, I got a cup of black coffee and free bacon roll (worth about £2 something)
The vouchers don't expire till end of the month, and are valid upto 11am each day.
Raid your nearest tube station/train/bus for leftover copies and stock up on the vouchers. I have about 30 from the District line this morning!
Claim the free bacon butty at Burger King