This is data from the Office of National Statistics. It is the Bank of England that is concerned with inflation figures, not the ONS.
This page seems to be talking about "the average household", and I think a median measure would be more informative for that.
To your CPI point though, I am not sure it makes sense. If the 1% of super rich are spending loads on yachts, and they are getting cheaper while food is getting more expensive, does that mean that state pensions and benefits should not go up as much, or that interest rates should stay low? I do not know the answer, but I cannot see why it should.