KLM have a 747 sim at AMS, but as they no longer fly classics it's probably no longer runnig.
The sim at GECAT is now owned by MK and it's going to be moved to the owner's premises by all accounts.
I supect GEACT or ALTEON could do you a private 747 course, but have you considered how much the base training will cost at about 10 grand an hour! You will have to fly a min of 6 circuits - 747 circuits are bl++dy huge. One extra circuit will cost you a grand and a half! And who will employ you on such a complex aircraft with one hour on type?