My understanding is that for this year, maybe only for UK, everyone arranges his travel personally except for Hotel; you have to book (directly not via Branch) the preselected hotel by the society.
Previous to this, the international conventions were part of a package that was offered by the society. I presume this has caused too much admin and complaints of expensive packages.
Now they get commission from Hotel bookings without any admin resources - sounds profitable!
And as always, donate for the the free buses/coaches at the assembly.