Unless I too am reading that wrong that puts the first confirmed cases 31 January. So assuming they had incubated and shown symptoms a few days before testing. So that puts them catching it and spreading it to approx 26th Jan. So did these cases catch it abroad or in the UK were they known to each other, guess we don’t know that.
From Wikipedia.
Late January 2020 – first cases
On 22 January, following a confirmed
case of COVID-19 in the United States the previous day, in a man returning to Washington from Wuhan, China, where there were 440 confirmed cases at the time, the DHSC and PHE raised the risk level from "very low" to "low". As a result,
Heathrow Airport received additional clinical support and tightened surveillance of the three direct flights that it received from Wuhan every week; each were to be met by a Port Health team with Mandarin and Cantonese language support. In addition, all airports in the UK were to make written guidance available for unwell travellers.
[37][38] Simultaneously, efforts to trace 2,000 people who had flown into the UK from Wuhan over the previous 14 days were made.
[39]
On 31 January, two members of a family of Chinese nationals staying in a hotel in
York, one of whom studied at the
University of York, became the first confirmed cases of COVID-19 in the UK. Upon confirmation, they were transferred from
Hull University Teaching Hospital to a specialist isolation facility, a designated High Consequence Infectious Diseases Unit in
Newcastle upon Tyne.
[4][40] The
index case for the UK, a 50-year-old female who had travelled from Hubei province and entered the UK on 23 January, had developed fever and fatigue after three days. Her close household contact, a 23-year-old student who had travelled from Hubei province on 6 January, developed symptoms on 28 January.
[41]
On the same day, an
evacuation flight from Wuhan landed at
RAF Brize Norton and the passengers, none of whom were showing symptoms, were taken to quarantine, in a staff residential block at
Arrowe Park Hospital on the
Wirral.
[42] There had previously been contention over whether the government should assist the repatriation of UK passport holders from the most affected areas in China, or restrict travel from affected regions altogether.
[43][44] Some British nationals in Wuhan had been informed that they could be evacuated but any spouses or children with mainland Chinese passports could not.
[45] This was later overturned, but the delay meant that some people missed the flight.
[42]