Another thing which you need to take note is that if you take up a contract through their website, you do get 14 days of 'cooling off' period but you must not have used the sim. From what I have gathered, how would 3 allow customer to 'try' first without allowing customers to insert the sim into the mobile phone? That is a tough cookie, isn't it?
What is important is that if you really want to take up a contract with 3, make sure you understand all their terms and conditions before you leave the shop! A good thing is that you need to have those promises made by the store assistance in black and white. If not, it is possible that they will not honour such promises! There could be a variation in what store assistants and through customer service.
However, if you take note of it, the best thing is to have a sim only contract with them. In such a case, you do not have a long contract and you can cancel the contract after giving 30 days of notice. You can also build up your loyalty points. I have to stress the point that 3 UK is not a bad service at all but the company's policies are crap, let alone their customer services through the phone!
I have gathered information that Vodafone UK is the most expensive mobile network provider in the country, followed by Orange, then O2, T-mobile and finally 3 UK. Although 3 UK offers the best deal in the current market, they will lock their phones to 'auto'. 3 is forcing customers to use 3G service rather than 2/2.5G service. What is unannouced is that if customers were to lock their phones to 2/2.5G, they will be using the Orange network because they do not have 2/2.5G services.
If you have bought a 3 UK phone, unlock it and then try to flash it to a generic firmware. It will allow you to lock to GSM networks. In this way, you will be able to save some battery life. Well, I mean a lot of battery life.