But 5 mins on any subreddit and you have people frothing at the mouth to hang every criminal.

5 minutes on any subreddit and you realise that you're more than likely speaking to a 14 year old in the US.

Last time I looked a majority of Brits support the death penalty. Which personally I've always found quite disturbing considering all the problems with it

I would agree this is disturbing but I am not aware of any mass poll on this topic that's not from a right wing fringe group / newspaper. Do you remember where you saw the claim that the majority of Brits support the death penalty?

So what do you think?

No the death penalty should not be reintroduced. I would support tougher sentencing, however. But additionally it should come with multiple programmes to increase social cohesion (youth activities, arts, sports, community outreach, education, quality jobs, etc, etc) such that being a hardened criminal is not a viable or attractive option in the first place. The death penalty as a deterrent to criminal activity did not work when we had it and doesn't work today either (see the US).