Ok, my problem appears to be finding a transformer!
Firstly, they seem to have different power ratings. Some are in amps,
some are in Watts, and some are in "VA"s whatever they are. Anyone
know how to work out one from the other.

VA is similar to watts, provided the power factor is corrected. If you fail
to correct the power factor, then the useful wattage goes down. All of this
is irrelevent to you, though.

What you need is a 12V *regulated* *DC* supply capable of at least 2A, or
24W continuous. It is best to overspecify a bit with regulated supplies, to
keep the temperature down, especially with a continuous duty cycle. Be
careful, some power supplies are rated at a reduced duty cycle, such as 50%.
The continuous rating will typically be a half or a third of the 50% rating.

Christian.