Congrats, hope the job is legit!
Check this official site out for info regarding EU citizens (Sweden counts).
UK Border Agency | European citizens
When you get to the UK, you can get 'pay as you go' phones, if you take an unlocked handset with you from Sweden, you can just buy a SIM card. (Unlocked = it is not tied to any particular network. Check in your mobile phone shop) for a relatively small amount of cash. Your friend should be able to help you choose or may be even able to get you a free SIM - I sometimes see offers on Yahoo etc for free SIMs from O2 for example.
I have O2 which allowed me to buy a one-off £4.99 (6Euro?) 'bolt-on' so I can text internationally for 10p (about 12Eurocents?) per SMS, might be worth it for you if you want to text home occasionally without worrying about costs.
There are other big providers there, Vodaphone, Three, Orange and probably more - I'm out of touch with it a bit now as I don't live theer.
Now I'm in Egypt, people in the UK can text my UK phone and I can read texts free, but I reply from my Egyptian phone as it's a lot cheaper.