flight training schools aren't. As it stands, they're not regulated by anyone at all.
What!? Yes they are. By the UK CAA and EASA.
Different schools also train to different standards. There are some schools which will train to a higher standard than the minimum and they make no secret of this. There are also schools which meet the absolute minimum standard. As long as they are the minimum that's all that matters to the CAA. In terms of the standard you want to receive and get yourself up to is your personal decision.
It's like flying Ryanair or British Airways. They both get you there it's just a different product.