Earlier quoted context omitted.
£35,000 salary in the UK has the same buying power (for want of a better expression as a $60,000 US salary. Adjust for "because London" and you're looking at £45/55K (not hard in London) equating to $75K - $100K. Thinking about it, I know a dozen or so people in the "poor deprived" north east of England earning over £40K who are under 30 years old so we're not all badly paid.
The difference is that Brits feel poor when they come to the US, whereas Americans feel rich when they come to the UK. Sure, PPP (Purchasing Power Parity) comparisions are important (e.g. it's easier to live in Thailand with $1000 per months than in NYC), but absolute values matter as well.
I.e. sure when you go to the US and have to buy USD with GBP you'l be at a disadvantage, or when you buy some electronics priced in USD, but how big a portion of your spending is that compared to food/rent/commuting/hobbies etc., all of which are priced in your local currency.