I would argue that most Western nations are no longer "wealthy" in that we don't have the raw materials and productive capacity to basically claim we are.
Let me be blunt: the UK has very little real wealth left, same as a lot of our European partners. We have tapped out most of our major natural resources and gone down the financial route, which is basically playing Monopoly while everyone else has to toil in the fields and work in the mines. The US is different, given their reserve currency status and mineral wealth still available. But poor old Europe...
I would say that without The City, the UK becomes a rather mediocre second tier economy. We primarily have GDP based on services, and a good chunk of those are services within the border. If people aren't washing money through the system in buying and selling stuff in pubs, shops and whatever else people do now (dog walking? Childcare? Media influencers?), then a good chunk of our wealth vanishes pretty quickly.