Day 2 test after return to the UK from Amber country - any good ones? any evidence of a price cap?

silvercar

nationwide Pathology are £40 and use Royal Mail priority boxes. The tests arrive with a pre paid envelope for their return.
I posted my results in time for the 4pm last collection and my results came back the following evening.

Adelelk

Is it mandatory to use one of the government approved companies or just recommended? Considering using Expert Medical for day 2, however slightly concerned this may be rejected at UK arrivals. 

onashoestring

The Government website says :

About providers and minimum standards

The providers listed on the Government’s list have declared they meet minimum standards for day 2 and day 8 tests (opens in new tab) Some providers may choose not to appear in this list. You can choose a different provider but you must check they meet minimum standards.

https://www.gov.uk/guidance/testing-on-day-2-and-day-8-for-international-arrivals