If you think this is "reasonable" based in one of the most expensive cities in the world, then good luck to you
Let's get this straight - it's
not based in the city is it? And therefore does not come with the stratospheric cost of living well there in terms of property. You would have to be utterly mad to base yourself in central London for a LGW job. There are plenty of towns and villages in the Sussex/Surrey countryside where £5k+ take home would get you a rather nice property.