BSL and part of GVA are indeed a sort of different dynamic. But you're still in the country where you are in, whether waiting in line to clear passport control or having just walked by the passport control after being cleared for entry.
Interesting point re embassies. In the past I recall that a foreign fugitive in a country was able to escape justice by getting to his country's embassy (or an embassy from a friendly country to their own), upon which the local police had no jurisdiction and could not arrest him/her. Isn't that how Julian Assange evaded any form of local arrest / extradition?
Embassies are not foreign soil. It's just that an embassy has a legally-privileged status vis-a-vis the host country based on the embassy being a recognized diplomatic facility for a recognized sovereign in the country hosting the embassy. That is why the UK couldn't just raid the Ecuadorian embassy to do a snatch job inside the premises -- although they did think about trying to snatch him if he were to stick his head/body out of a window or onto a balcony. If it was a consulate, rather than an embassy, it's even less privileged than an embassy in terms of action vis-a-vis the hosting country's authorities; but even then its sort of privileged from host country action. Whether or not an embassy-hosting country is willing to violate international law vis-a-vis an embassy recognized as such by the host country, the host-country's recognized foreign embassies are not foreign soil. The hosted embassies are just legally privileged on the soil of the country hosting them.