If you read your own link, it explains that the entire point of estimating owner' equivalent rent is to avoid counting capital appreciation of housing in the CP

If you read your own link, it explains that the entire point of estimating owner' equivalent rent is to avoid counting capital appreciation of housing in the CPI, because house prices are not consumption (and also because actual expenditure on mortgages would be particularly unhelpful to include in an inflation index because it's directly correlated with the policy variable central banks use to reduce inflation) In the UK, the subject of the OP, measured inflation is around 8% and house prices (which rose consistently above inflation for the last couple of decades) are falling. Falling house prices are not good for homeowners.