Yes, I have contacted most of the schools listed in the NMC's website but most of them directed me to their website to apply online.
I think you're right though, it might be uni to uni policies as some of them offer placements attached to their programmes (like South London College and Manchester Metropolitan University) while others offer only the 20 days of protected learning time.
Although I've also heard about non-EU nurses getting approved despite lacking a few hours, I think that maybe NMC will consider the application if the difference isn't more than a 50. I am not entirely sure about it though as it's only based on hearsay. I am from the Philippines by the way and here are my hours..
Theoretical Hours: 2,718 (NMC requires 2,300)
Clinical Hours: 2,314 (NMC requires 1,533)
Lastly, do you happen to know a list or a website of supervised practice placement providers here in London?
Thanks and have a Merry Christmas!