Hey all
Just thought I'd share this:
I purchased a £10 Vodafone top-up voucher from Tesco's today - get back home and relised that I cant remember getting it at all. I was in a hurry and when they asked me "would I like a receipt" I say no and leave.
Anyway, I phoned up the local store - which they were very helpful (and said that it happens a lot), they cancelled the transaction, and will re-issue another one of which I will pick up tomorrow.
There you go, money not down the drain 
Cheers