My 3 sim only contract was coming to an end so I called up 3 asking for an offer. I quoted an offer from EE which I was going to leave them for if they couldn't beat it (see below).http://www.hotukdeals.com/deals/ee-16gb-data-unlimited-mins-unlimited-texts-sim-only-12-month-contract-was-34-99-2486239
They offered me 30gb data and unlimited mins for £20 pm which I didnt want (the amazon voucher from EE beat 3), he admitted that was the best he could do so I told him I was leaving and asked for a PAC code to keep my number.
I was then transferred to another guy who offered me a rolling contract with a special one time price for me as I've been with 3 for years, 8gb data unlim mins + texts for £13pm. I took this offer.
Note: I have been with 3 for a long time so this is unlikely to be offered to a newer customer. Also you do not get a personal hotspot (no tethering) and NO FEEL AT HOME. So thats a bummer do there is no contract so I can still leave at any point.