Well in my case bad habits did start and persist through Skate UK, Passport and beyond. But maybe I took too long over Skate UK. But honestly at the rinks I skate at a lot of the adults, including me, are a bit lacking in the basics. Maybe we should blame the private coaches. But I do think that there is often a general sloppiness about the way skating is taught and approached, especially for adults. I know we generally learn slower but that doesn't mean we can't learn to do things with precision.
So how much time did you spend on Skate UK and did you have a private coach as well during any of that time? And how big were the groups in Skate UK? If you only get a minutes worth of personal coaching time a week as I did in my rinks equivalent of Skate UK due to numbers in the group (over 25 skaters for the lower grades) then obviously there is no way you can learn all the basics well in that time - it all takes practice time which most people just doing Skate UK don't have or are not at that stage, willing to give to skating.
Private coaches should indeed be concerned that their skaters understand the basics but you do need to be doing other stuff too - and often trying harder things makes the stuff at your level suddenly seem easier.
That seems to be an argument for getting people through Skate UK as quickly as possible without worrying over much as to quality so they can then get decent private coaching and be sure to be practising things as correctly as possible for their standard.
Nobody is arguing that basics aren't vitally important but I don't think you can expect Skate UK to be the place to learn things to NISA level 1 and beyond standards.
There are definitely still private coaches around that don't think adults should be skating and don't bother to push them but there are also plenty that do believe adults can skate and skate well and will push them the same as the kids if that is what they want.