"The number of people in employment in the UK is measured by the Labour Force Survey (LFS) and consists of people aged 16 years and over who did one hour or more of paid work per week and those who had a job that they were temporarily away from (for example, because they were on holiday or off sick). The largest two categories within employment are employees and self-employed people; in recent years these two categories have accounted for over 99% of all people in employment."
The "self-employment" rate, which mainly consist of various low-paying gig jobs without the welfare benefits of a full-time job, is growing and growing: it was 12% in 2001 and 15% in 2017. And there's this poignantly beautiful graph about income distribution between full-time employees and self-employed people in Figure 3 in this ORS article: https://www.ons.gov.uk/employmentandlabourmarket/peopleinwor.... Ah, I like it when distribution graphs clearly tell more about economic situations than single-number statistics.
One should understand that the overall decreasing quality of jobs (and wealth inequality created by those crappier jobs) are really the main problem. Unemployment rates (in the definition that neoliberal governments use) are more of a propaganda at this point.
As I said elsewhere underemployment has been falling as well.
The official ONS definition - which anyone can check on the ONS site - counts anyone who works one hour a week as employed.
The figures also include anyone who is self-employed for tax purposes, whether or not they have any income from work.
If we used 1970s metrics, where employment was defined as having a full-time job that comfortably covered basic living expenses, unemployment would be running at absolutely terrifying levels.