Savvy not chavvy
T-Mobile, ASDA, Virgin, Tesco for chavs? Particuarly ASDA, I would say they are for users that don't want to get screwed on call costs.
Personally I'm on 3 wiht my TyTN II and love them - PAYG so I can jump ship if the CS cause me grief.
Personally, I prefer the 'get your own phone & PAYG' option as contracts are too risky if you accidently go over an allowance. No tie in, can't land you with large bills and loads of good deals and bonus's for topping up make contracts for mugs.
Sim free Nexus One = £500 equates to £27 per month over 18 months
Add a decent PAYG SIM such as 3 @ £10 pm (which includes 150Gb data and 200 txt for each topup)
Work out how much you pay for contracts v's cost of sim free handset and there isn't much in it.
As for the comment earlier about 3 not doing Android, as already pointed out, the do the Hero and are in talks to supply the Nexus.