Just got an email from Pitcher and Piano offering a free pint of Estrella Damm (edit: worth £3.95) with a printable voucher. I've never tried the stuff, but seems like very good deal - last time I was in Pitcher and Piano, a pint of Heineken was about four quid.
You should be able to get it by signing up to the newsletter list on their website. Valid until 28th February, and not much reason you couldn't use more than one voucher.
A good newsletter to bee signed up to - had a free bottle of Bud not so long ago which would normally been £3.50ish.