The average cost per bedroom for a week in London in July and August is £711, a survey by TripAdvisor showed, more than three times more expensive than some other parts of the country.
Similar costs in Yorkshire are £217 per room, with the Scottish Highlands (£229), North Wales (£237) and Cumbria (£242) also offering good value for money.
The cheapest in the survey is Croatia's Dalmatian Coast (£264 per room) followed by Andalucia in Spain (£274) and the Canary Islands which include Tenerife (£281).
'Holiday rentals are always a great option,' said TripAdvisor spokeswoman Laurel Greatrix.
'Cost-conscious travellers - especially those travelling in groups - should look to destinations like Yorkshire and the Scottish Highlands in the UK, and Croatia and Andalucia in Europe, to find great properties without breaking the bank.'