The NHS will not provide tests for travel.
Only a PCR test is acceptable (a list of private test providers can be found here)
Full rules and eligibility can be found here: uk.ambafrance.org/COVID-19-Conditions-de-deplacement-entre-la-France-et-le-Royaume-Uni-28925.
Please check carefully as anyone not meeting the criteria will not be permitted to travel.
Please note there is NO COVID-19 testing facility at Eurotunnel.