What on earth has caused the mixer to go from £24 to £48 in the UK?
tariffs most likely
Strange, but everything else is still the same price.
Seems like the tank has significantly jumped in price too. 
It makes sense, machines are cheaper now and they are supposed to come with OML already. We will not be using Original resins, but since tanks are proprietary they need to keep profiting from any source.
I was told by Form Labs that when they lowered the price on the Form 4 a couple months ago, they had to raise the price on some other items like wipers and vats.