Well I'm grumpy now. I finally reached the end of my Three contract and cancelled, put the SIM into my phone to test Voxi in the B535-232 and got 100Mbit off Three on my phone.
Put the SIM back into the B535-232 and its doing 60-70Mbit.
Yet real-world usage I'm still struggling to get over 30Mbit.
Firstly, is the B535-232 a piece of junk?
Secondly, are Three taking the pee and prioritising speedtest.net servers? This rather suggests they have a ton of spare bandwidth they are deliberately throttling back.
The strange thing is, I could have sworn I got 100Mbit once or twice on Three using the B535-232 when I first got it.