That depends what you mean by "being" middle class. If it's a question of your self-image, then sure, you're working class. But someone else might look at you and define you in their own terms as being MC.
Statisticians (and marketing people) probably wouldn't use the term 'middle class' at all, but something like 'Social Grade': A, B, C1, C2, D or E. These are based on your occupation (or that of the household's main income earner). The first two and last two are lumped together for the census, so in 2021 there were:
- AB: higher and intermediate managerial, administrative and professional occupations (23.3%, 10.9 million people)
- C1: supervisory, clerical, and junior managerial, administrative and professional occupations (32.8%, 15.3 million people)
- C2: skilled manual occupations (21.3%, 10.0 million people)
- DE: semi-skilled and unskilled manual occupations, unemployed and lowest grade occupations (22.6%, 10.6 million people)
Class is more complicated that just your job, of course. You could be a titled aristocrat who works as an electrician when not sitting on the board of an arts organisation, in which case placing you in Social Grade C2 doesn't really tell the whole story. And these categories are only somewhat correlated with income.
If a plumber sets up a limited company to manage his solo business, then takes on a labourer, and an apprentice, and employs a part time administrator to manage payments and keep accounts, and eventually ends up as millionaire owner/CEO of something like Pimlico Plumbers, then when exactly do they stop being counted as a C2 skilled manual occupation and become AB?
Really there is no single answer to the question of what 'middle class' means. It means you're somewhere between 'working class' and 'upper class'. Given that fewer and fewer people in the UK are in low- and unskilled manual occupations and a vanishingly small proportion have ever been really upper class, I'd say a large majority of people could be considered MC, even if that doesn't fit with their self image.