I'm not too sure whether this is worth posting or not, but there's a voucher in the current issue of love it!, which costs 71p, for a free Shaken Udder milkshake worth £1.35. There are further details on the love it! website
On the website it states that the voucher is valid at MAIN branches of Tesco, Waitrose and Sainsbury’s, but on the voucher in the magazine it just states MAIN branches of Morrisons & Sainsbury's.
'...luck came to those who left a space for it.' Terry Pratchett