Hazir, there's two unrelated issues at hand here. The first is that the UK has done a reasonably good job of sourcing doses and getting shots into arms. I'd say they have done as well or better than any other large Western country, though I expect the US to overtake them in time. This should be celebrated as a success on vaccine rollout, though I don't feel the need to draw explicit comparison with e.g. the EU. I do not think they are being reckless in working to get their population vaccinated as quickly as possible, though I may have some quibbles about the quality of the data used to support the AZN authorization at the time of authorization and its use on older patients (I would have prioritized Pfizer doses for those patients and used AZN for e.g. healthcare workers).
The second is their choice on dosing strategy, which I find scientifically unfounded and risky. This is an experiment, true, but not one we are likely to learn anything useful from. I certainly hope that the UK is successful in its strategy and think that on the balance it will probably still 'work', though we will likely never know if it will work as well as following the as tested strategy.
There are many other things to criticize the UK about regarding their pandemic response, though they are hardly unique in this regard. But I wouldn't criticize them for the alacrity with which they are vaccinating people, just the dosing regime they have chosen without adequate supporting evidence.