Public transport:
Vastly better, in terms of coverage and frequency of service, than almost anywhere else in the UK (and on at least a par with many other international capitals). However peak time travel often means experiencing considerable overcrowding. (Not anywhere as bad as Tokyo but still fairly unpleasant). Getting to know the tricks of travelling can help. (e.g. boarding the very front, or very back carriage, of a Tube train will often enable you to find a seat while those in the centre carriages all have their noses pressed into someone else's armpits).
Work:
Rates of pay in many (but not all) jobs are often higher than elsewhere in the country. For example, here in East Anglia, a warehouse supervisor with twenty staff under him will probably earn £6.50 to £7.00 per hour. Around Heathrow, the pay rate for that job would be around three times that amount. However higher pay is negatively offset by . . .
Housing costs:
For the vast majority of Londoners, buying a property is probably out of the question. Renting is more common than elsewhere in the UK but it's still expensive. For example, I saw an ad yesterday for a one-bedroom flat in central London (but not in a particularly 'posh' area) at £420 per week. You can pay far less in the 'grottier' areas around the fringes of London (e.g. Dagenham) but it could still be at least double the price of housing in other parts of the UK.
Hustle & bustle:
Yes loads of it. You can't avoid it and you either love it or loathe it. However London does have more green space, for unwinding, than most other big cities across the world.
Cost of living:
Your shopping bill in a London branch of Asda or Tesco won't be any more than in Sheffield or Bristol but 'luxuries', like beer, might cost rather more. (Expect to pay £3.50 to £4.00 per pint for bitter, or basic lager, in many places but there are ch