ok something I know about for once on here, as some of you know I have been in the phone business for about 12 years now (blatent plug for what I do
http://www.remoteunlocker.com) , and although I don't now, used to sell contracts on all the networks, so have had dealings with them all, here's what I think:
'3' Don't bother, coverage is rubbish, customer service - errm, do they have any?
T-Mobile Bad coverage compared to the others (bear in mind Virgin & BT use T-mobile if you are thinking about going with either of those), customer service ok ish but are expensive
Orange - 5 years ago I would have said they were cheapest, free insurance was excellent, customer service brilliant, unfortunately I hear more and more horror stories about them now, so possibly they have slipped recently.
Vodafone, rarely get problems with customer service, coverare good, pricing is pretty good
o2 - I'm with o2 which should tell you a fair bit. 5 years ago I wouldn't have touched them, CS was bad, and prices were worse, but now you get through to someone usually straight away & most problems are sorted straight away. I had a fault on my 8 month old v3 last week, posted it away for repair Monday had it back Thursday, pricing is now very good too, especially their online deals,
http://www.o2.co.uk .
However it's worth noting you can always find someone who has had trouble with any company.
Kathy, if you move all your handsets to o2, you might want to look at the business tariffs, one for example give completely free calls to any other o2 mobile, so if you have 15 phones and call each other that might save a lot of money if you move them all to them, if you already have phones and want sim only deals you will probably find if you call them they will reduce the line rental too. If you aren't changing them all, have a look at
http://shop.o2.co.uk/shop/o2uk/jsp/tariffs...ef=SIM_mod_head where you have 30 day contracts and double minutes and texts for however long you stay with them. Business tariffs are here
http://www.o2extras.co.uk/business/ - if you do want 15 handsets though ring them as they will offer you a deal to get the business, hope that helps a bit
I know a manager of an orange shop too, if i see him online ill get him to read this thread and see if he can suggest a solution for you - whereabouts in the country are you (in case you are local to him
)