I don't know man, I'm with user5994461, after all my bills monthly ($2,000 monthly rent, $350 new car, $200 insurance, $30 phone, $200~ utilities, ~$500 food) I have +/- $60,000 USD at the end of the year after taxes in surplus with only one year of experience and no diploma..
You can't, because if you're American and you work in the UK, you'll have to pay taxes in your home country on top of your British taxes. That will ruin whatever compensation you have.
Please. Let's leave Europe to European and USA to the USA. No cross continent comparison.