Oh that's crazy, I didn't know telephony all changed around there! Thank you for reading it so much and in such detail to have picked up on that, I'm releasing a new thing soon and I'd be super happy if you looked at that too :)
If you want a detailed look at the UK dialling codes then you might find this useful:
https://en.wikipedia.org/wiki/List_of_dialling_codes_in_the_United_Kingdom
I'm honoured that you want me to have a look at your next project.