Cable Forum - Buying mobile contracts online

Just curious if anyone has signed up to mobile contracts from independent mobile retailers over the internet or phone, other than well known ones like CarphoneWarehouse or official network's websites.

I mean sites like dial-a-phone or mobilephonesdirect.co.uk

Is there any drawback in going through them as opposed to more established retailers?

I've found that some of these sites offer much better tarriffs that aren't available directly through the network provider or in high street retailers. Also one of the main reasons I'm tempted by them is a lot of them offer TWELVE month contracts which is hard to come by these days, I hate having to sign my life away and be stuck with a phone for 18 or 24 months

Any reasons why I shouldn't buy from these websites?? anyone have any good or bad experiences with them?

I'm looking at this one in particular;

http://www.mobilephonesdirect.co.uk/...FU0A4wodz0p7_A

Help/advice would be appreciated. Thanks