quick update.
for anyone in my position (no UK power adapters and everything rapidly dying)
walking south on Forida, turn right onto Corrientes, just past the street newsstand there is a hatch in the wall (a sort of newsstand with electronics) which sell the adapters (15 pesos each). cheap and cheerful - perhaps don't leave them plugged in whilst you are out for safety.
thanks to all for your advice in relation to this.
and the food info and potential debate is an eye opener. I have much work to do it seems - all info here is a great start! thanks.