I would love to hear from people who have studied biology or epidemeology how valid the methods of detection are. From what I can tell they haven't actually isolated this virus and they have concluded that it exists using data analysis only:

"The new variant was detected in early December 2020, combining genome data with knowledge that the rates of infection in Kent were not falling despite national restrictions.[4]

The two earliest genomes that belong to the B.1.1.7 lineage were collected on 20 September 2020 in Kent and another on 21 September 2020 in Greater London.[14] These sequences were submitted to the GISAID sequence database (sequence accessions EPI_ISL_601443 and EPI_ISL_581117 respectively). As of 15 December, there were 1623 genomes in the B.1.1.7 lineage. Of these 519 were sampled in Greater London, 555 in Kent, 545 in other regions of the UK including both Scotland and Wales, and 4 in other countries.[14]

Backwards tracing using genetic evidence suggests this new variant emerged in September 2020 and then circulated at very low levels in the population until mid-November. The increase in cases linked to the new variant first became apparent in late November when Public Health England (PHE) was investigating why infection rates in Kent were not falling despite national restrictions. PHE then discovered a cluster linked to this variant spreading rapidly into London and Essex.[15]

Although the variant was first detected in Kent, it may never be known where it originated. Discovery in the UK may merely reflect that the UK does more sequencing than many other countries. It has been suggested that the variant may have originated in a chronically infected immunocompromised person, giving the virus a long time to replicate and evolve.[16][4]"