I'd imagine that in the UK things aren't so bad, but in other places MM times apparently get horrendous during off-peak times...
I think it's time 343i let people choose if they want to region-lock themselves, or deal with Latency when playing with others who opt-in to playing out-of-region.
I'm in Germany and I didn't have any issues finding matches between 10am - 3am for the whole last Season.
What they should have done was giving us the server selection like they actually wanted at first, but with the option to play Global, if you really wanted.