These can only be used in Japan to operate UK electrical equipment if you are relocating or living there. The 1500V version was able to run a TV, DVD and surround system. I have 2x 1500V (price £100) transformers, half price to new.
From the Airlink website -
Use UK electronic equipment in Japan
230V output to run British appliances in Japan
100v Input fitted with Japanese 3pin plug
Conforms BSEN61558-2-13 CE & RoHS
All transformers from 1kVA and above, are fitted with surge limiters
British Built