According to the latest ONS figures, over one million people were estimated to be suffering from 'long Covid' in the UK in the four weeks ending 5 September. Long Covid is defined as "symptoms persisting more than four weeks after the first suspected coronavirus episode that are not explained by something else". As this chart shows, while 394 thousand say that this does not restrict them in their daily activities, 706 thousand are experiencing some degree of problems in this regard.
Note that these figures represent symptoms "as experienced by study participants, rather than clinically diagnosed ongoing symptomatic Covid-19 or post-Covid-19 syndrome." The source adds that while "there is no universally agreed definition of long Covid" but it covers a broad range of symptoms such as fatigue, muscle ache, nausea, abdominal pain, shortness of breath and loss of smell.