Of currency valuations and their effects on purchasing power

Sometimes it is useful to remind ourselves the enormous welfare effects of currency valuations.
I spent most of the afternoon working on GDP data across a panel of 27 European countries, from 1993 to 2017. I was attempting to test a old hypothesis of mine on the effect of income convergence on identification with Europe.
After much dataworking, I realised something was wrong in the dataset: the UK, for instance, had reported a 23% growth rate from 1996 to 1997!
I frowned, and spent the remaining afternoon trying to look up the source of the problem.
It wasn't calculation on my side.
It wasn't a transcription mistake from the original excel workbook to stata.
it wasn't the in the original source of data (the same 23% was posted on Eurostat).
Tu put it bluntly, I was stuck. Then a sudden illumination in the fogs of Albion: as a matter of fact, the Eurostat data were..... in Euro. But the UK's currency is the Pound. Was it a valuation effect?

Indeed, it was a valuation effect. As it happened, the European currencies remained stable from 1996 to 1998, with the exception of the Pound, which- being a reserve currency- enjoyed strong capital inflows due to the South-East financial crisis. As the pound appreciated vis-à-vis the ECU, the purchasing power of British production - expressed in terms of ECU- grew substantially. As the ECU lost 19% in 1 year against the Pound, the mere 4% nominal growth rate of the UK (in Pounds) became 23%.... in ECUs. Of a sudden, British household were able to enjoy much higher consumption out of thin air, even though their real GDP rate was about 2.5%.

In other words: it doesn't only matter how much you produce, but what that production can buy. A weaker currency makes your own costs cheaper for abroad, but ultimately a strong currency allows you to buy more, producing less. As the UK did from that period onwards.

It wasn't a lost afternoon, after all. Was it?