I will have to mention that this varies all over, especially the bit older generation (not exclusively though) also has some weird quirks language wise. So while they might speak and understand the English language quite well the are some parts missing. As an example I like to mention the phrasing of Bolkenstein (a Dutch National/EU politician) of economic handouts to people as "Golden showers". So while proficiency might be high, it's not always ... perfect.