I have successfully moved to Netherlands and then subsequently redeemed and earned 241's from a U.K. AMEX. No problems.
When I redeemed, I had to use it ex-UK though the agent was able to book the ex-EU at the same time (not 241) and 'link' the bookings but the taxes were ex-UK.
When I cancelled my UK AMEX I was given the usual spiel about needing a BA AMEX to pay for the flights (not necessarily in my name.) However, I thought it best to keep the free BA card incase a U.K. AMEX is needed instead of my NL one. At first I thought they wouldn't be able to tell but then the billing address is not UK.