I've changed my country in my Main Account Page and ensure that it's synced with individual projects.

My project stats now show my country as Netherlands but detailed stats overview page it still shows Resident of United Kingdom.

How can I get that to update to match Netherlands as per other projects?

FYI, I did post this in CPID problems but maybe this is the more appropriate place.

AFAIK the overall country stats are not calculated 'on the fly', but only once a day. So be patient and keep an eye on https://boincstats.com/en/page/boincstatsStats

I actually updated everything more than two weeks ago, so the once a day thing wouldn't be the answer.

Any other ideas?

Just checking again: did you also change the country in https://boincstats.com/en/bam/account/ ?
I also noted that all your 23 Closed Projects are still pointing to UK. Maybe you need to use the BAM!-specific feature "Sync retired projects", but I am not sure if that's doing what you want for the switch of countries.

I did update https://boincstats.com/en/bam/account/ already.

I also went into https://boincstats.com/en/bam/retiredProjects/ and synced there. That only has four projects listed still, all of which have country as Netherlands.

Have you verified your country at each active projects web site are all showing Netherlands?

Yep, that's the same across all still-running projects that I can find. There are no active projects that still have the old country.