Going back to the OP's query. My Father did two spells with NATO in Europe (He was in the RAF), one in France and one in Belgium. On both occasions he brought back stuff he had bought over there and it worked quite happily in the UK and this was back in the days before the EU when the continent was 220V and UK was 240V. The only "problem" was the need to change the plugs - or at least get a 2 pin to 3 pin adaptor.

The tolerances were such that the difference between the UK and continental Europe was of no great significance.