Not sure I agree with "'rising as % of GDP' graphs/facts". It has actually been in a downward trend since 1950, when it peaked.
https://www.instituteforgovernment.org.uk/publication/whitehall-monitor-2021/finances
As @Bozza says, just because rising, doesn't mean not low. Also rising in absolute terms, but not compared to GDP.
https://www.gov.uk/government/statistics/hmrc-tax-and-nics-receipts-for-the-uk/hmrc-tax-receipts-and-national-insurance-contributions-for-the-uk-new-annual-bulletin