Of course, The UK Pint is 20 fluid ounces (volume), which in the case of water is 20 ounces (weight).
Easily remembered
"A pint of water
Is a pound and a quarter" (i.e 16ounces + 4 ounces)
Thus if a cup is 8 fluid ounces, for water it is half a pound.

For those who still think in old measures, a 'Bottle' of scotch or other spirits used to contain 26+2/3 fluid ounces. Whilst this appeared a strange measure, it was One and a third pints, a standard measure (a single) was 1/6th of a gill (a gill being a 1/4 of a pint) Meaning that a bottle held exactly 32 measures. Nigel