In reply to Kemics:
I recently used one of these companies (affordablemobiles.co.uk) after reviewing all the deals on here:
http://www.moneysupermarket.com
I wasn't after an iphone as I had a recent warranty replacement on an android phone, and quite fancied a deal with a cheaper tariff, and a free gift (android tablet).
Stupidly I didn't really look at the reviews, and instead trusted money supermarket (mistakenly thinking it was moneysavingexpert.com).
After completing the purchase on line, I then for some reason googled Affordable mobiles, and the reviews were horrendous, especially relating to free gifts, customer service etc.
I therefore panicked that I'd been done, the cheap phone turned up the next day however, along with a note saying the free gift would be dispatched in the near future. (exactly as predicted in the poor reviews)
A week more panicking, and deliberately not opening the seal on the phone or simcard in case I needed to appeal to Orange, and to my surprise my tablet turned up.
Therefore I cannot fault this company, and yours may well be fine too. I remember looking into the company and finding it had been taken over a year or so ago (I forget who by) and I think most of the poor reviews related to the previous management. However, not knowing what deal you are looking at, I would strongly advise against any deal that reduces the line rental via cash back, as this seems to be the source of a lot of the bad reviews, and you have to be very on the ball and diligent to get all of your cash back redemptions (like sending in your 3rd, 5th, 7th bills along with appropriate voucher and waiting for a cheque).
On the face of it my deal was too good to be true, but was - "Free" phone - cheapish android smart phone, Good Tariff deal (for me) 900mins, unlimited txts, 1GB data, and a Sony Xperia Tablet S for £23.50pm (no cashback) 24month contract.
Remember only people who have bad experiences are more likely to put up reviews than those where it went as expected.
If you are just going for a phone and contract, there is little they can do wrong other than not send you the phone, or put you on the wrong tariff, both of these things can be resolved with the phone company's assistance (and use of the sale of goods act)