There will always be the exception that goes rogue and to extremes but my gut feeling is that on the whole UK police are quite restrained, profession and well trained. There is also a thorough system for bringing those who abuse their power to account. Of course your average on the street 'bobby' doesn't carry guns anyway.
I get the feeling that in the USA there may be more trigger happy cops around. Not very knowledgable on Australia.
However, the amount of out of control police here in HK does seem fairly extreme. I have viewed countless excess and unnecessary violence videos around on the internet.
e.g. https://twitter.com/casliveas1/status/1197588289772900354?s=20