British police aren't perfect, but I'd trust them more than police from most other countries. When Sir Robert Peel founded the Metropolitan Police in 1829, he based it on the "Peelian principles" - the idea that the police operate with the consent of society as a whole. Policing in the rest of the country followed the same model.
The Met is probably the worst example of a British police force. They shot de Menezes in the head for no reason, killed Ian Tomlinson for no reason, they racially profile constantly, failed to convict the Stephen Lawrence killers because they were institutionally racist, they're brutal during protests (c.f. kettling) and when the riots kicked off they basically just ran away with their tail between their legs.
https://en.wikipedia.org/wiki/Peelian_principles
These principles are still mostly respected today.