For the British here is a link to the Government list of suppliers of tests from £49. I found one Day 2 and Day 8 test provider for £110 for those returning to the UK from any Amber list country: https://www.find-travel-test-provider.service.gov.uk/test-type/amber.

This is the lates map of countries from the pespective of the Czech Republic Map of countries in Europe 11th June 2021   Rules for Entry 1st June 2021