UK & Guinea plausibility/ndc list fixes

@floere one more for you.

* UK's mobile ndc listing just happened to mostly work by luck (the 1.8 compatibility around splats)
* I originally based Guinea's around that code on the incorrect assumption it was actually proper
* Also removed the `fixed(n)` cases from UK and Guinea for better plausibility testing.

Interesting note: Ofcom (the UK body that administers phone number assignment, among other things) has lists of all the allocated ndcs and their number lengths (e.g. 4+5 vs 4+6 vs mixed) that are supposedly updated weekly. When making the `fixed(n)` => `none` change for the UK, I hacked together a test case that ran through every allocation and tested plausibility. So now +44 numbers aren't considered plausible simply by being 10 digits long (excluding country code), and with pretty decent confidence that numbers that are valid will all be considered plausible.