Below that to be honest. Is it possible to get something for £500? I had been looking at Thick as Thieves in LA which I could get for around £450 shipped to the UK. I feel its a little risky though if theres something majorly wrong with the fit and I'm stuck in another country.
No need to do that. Go to someone like Cad & the Dandy or Suit Supply in London. They both offer MTM suits around the £500 mark, and they'll measure you personally. All it'll take is half a day of your time and a return train ticket. Less risky than online MTM. There are no doubt other options in London too which will have been discussed here before - use the search feature.