$5000 doesn't exactly match the tag line you posted. Sadly, if you are restricted to steel shot, you have few options, BUT, I would say the few options are better than just about any option out of Merry England, sorry, Salopian-do you feed steel to your Purdeys? Doubtful.
The RBL would work, but, it is a 20, and 12 gauge ammunition is easier to come by in most of the world, not to mention 20 gauge steel shot loads leave plenty to be desired on wild fur and feathers. The Gold Label solves both problems. Good luck finding one. The Red Label is a trooper (usually), and I read years ago that none other than Holland and Holland used these guns at their shooting school. I'd pass on the hardware store gun idea, most of them are getting pretty old, while a good 'smith isn't that tough to come up with here, it might be a problem over there. I can imagine some poor Danish 'smith opening up a broken Parker and saying to himself, " what the hell is all this stuff in here for?"
However, one other option remains-the Winchester 21. You could relieve the chokes to a bit less than modified, and rest assured that newer steel loads wouldn't harm the gun. It is as "All American" as they come, and a clean example in 12 could be found under budget. Have a 'smith service it, and 3 years should be a walk in the park for a 21. I'd prefer the double trigger/extractor version to the later and more complex single trigger/ejector, but, either in 12 gauge should make the grade. Bring a Winchester lever action in 45-70 with open sights, and I bet you are covered for anything you might find, and will impress the natives
Have fun. Sounds like a great experince if the work you do doesn't suck.
Best,
Ted