If your going to be in the UK for more than 12 months and your thinking of buying a cell phone, you will be better off getting on a plan in the UK rather than buy a phone in Singapore.
Cell phones are cheaper here in Singapore than in NZ but the mobile industry is so competitive in the UK that you can get a really good phone free if you sign up to a 12-month plan. And the plans are much better than in NZ too (comparative to income of course). I was paying 25 pounds a month and got 100 sms, 200 anytime, cross network, carry over minutes per month.
I found "Phones4You" in the UK had the best deals.