I had assumed that "Defunding the police" made a lot more sense in the US than in the UK. Similarly with prisons, as a matter of fact. In the US certainly a lot of prisons are privately-run, accounting for just under 10% of the prison population. Private control of prisons shouldn't really exist, because the goal of prison is presumably not to run it at a profit.
As to policing, the slogan might have been better-expressed as "reallocate some of the spending that goes towards police forces for unnecessary excesses such as surplus military equipment to other social programmes that have a demonstrable benefit in reducing crime levels in the first place". But that is less snappy.