If you are a software developer with any experience, do not accept anything under 80k USD, or 50k pounds in any major city.
UK gas prices are currently 4 pounds a gallon, or $6.34 a gallon. We pay 1/3 of that here in the US. Even with the recession 80k is the minimum salary for a developer with any seniority. If there wasn't a recession it would be 100k.
You have to consider that if you are ever terminated at 30k pounds, your unemployment checks will be super low. Too little to live on in any area. I recommend finding a better job first.
You should also seek an employer that lets you travel on their expense tab, and pays for your laptop, pda, cell, outside training and conference admission fees. This is not extraordinary but normal for any mid to large sized company. Don't cheat yourself by accepting a lesser job.