Can I validate UK, Norwegian, or Swiss VAT numbers?

No — those are outside VIES, so vatnode does not validate GB, NO, or CH VAT numbers. Their VAT rates and number formats are available in the rates reference data, but there's no live number validation for them, and none is planned since it would need each country's own registry rather than VIES. Northern Ireland businesses trading in goods with the EU use the XI prefix and are fully validated through VIES — full country-by-country detail is in the coverage reference.