If you're ever going to work in the uk market then it's a no brainer to have the .co.uk extension to target a uk market, also if brand building it's also a no brainer to ensure you have the essential extensions. If you don't take the .co.uk extension then that leaves it open to another business to come in and use that .co.uk extension.
You obviously see it as important to have a .com despite being in Holland and you're targetting english speaking people, considering the UK is the home of the English language then registering the domain would be another good move. I'm struggling to understand why you wouldn't register, perhaps I should just ask you that?