Yeah it's quite a good money maker for some of the larger independent stores, I think the only reason the networks have started doing it themselves, is so they can avoid having to pay out the large commissions to others. But like I said, avoid the unknown independent places, Birmingham's largest one (Mobile Connections) pulled a fast one within the last two weeks, leaving potentially thousands of people with massive monthly line rentals. A friend of mine had an offer from them where he paid line rental for one phone, but was given two more for 'free' which the shop paid for. However, he's now stuck with a £175 monthly line rental bill.
A new shop opened at the place Mobile Connections used to be, and yeah, you guessed it, it was another phone shop :|. Whether connected to the old store is yet to be seen, but the old store owners must have walked away with at least £1m worth of commission and most likely some of their phone stocks.