I wouldn't bother - it's such a short flight that it will hardly make a difference (if I recall correctly from my last flights in BA economy, the seats on such short flights are the same, minus some extra room due to the middle seat not being used).

If you don't need the extra baggage allowance offered in CE, I wouldn't go for it (unless you're dying to visit the lounge at AMS - I have no idea if that would be worth £69, but from my experiences with lounges, I would assume it is not).

The CE product is surely worth it in my book for flights from LHR to the States (the only flights other than STR-LHR I've done in CE so far - the flights from Stuttgart to Heathrow were all fine, but surely not worth an upgrade). If your flight is only within Europe and not connecting to a longer flight in CE, I'd save the money and spend it on a nice dinner instead.

Martin