I've got a Tesco mobile sim card that I don't need any longer with a balance of £20.32
It's still active and Tesco uses O2 network, so coverage is the same.
I only gave the number out to one person and I have had it for about 2 years so I imagine any wrong numbers have probably fizzelled out. The number ends 339440, so quite memorable.
PM me if anyone wants to know the exact number.
I have 100% positive feedback on ebay (username guydjemal).
Looking for £16.00 inc delivery via first class post.