I wanted to switch from my current Virgin contract of £10 a month to the Tesco deal, phoned up Virgin and said I want my PAC code so I can swap to Tesco and they said they have a deal just for people swapping to compete against the Tesco deal.
They are giving their usual £20/month contract for £10 a month. I got changed to it straight away from my other contract.
Not sure if you already need a pay monthly contract with them or if you could just phone up with a pay as you go sim. Definitely worth a try though!
The unlimited internet has a fair usage of 1 gig/month.
RETENTIONS DEAL FOR EXISTING CUSTOMERS.