Your post doesn’t make it clear whether the stop is on the same day as you travel to the UK which would be fine - but here are the basics:

With every global pass you are allowed one day to journey out of your home country and one back in. These can be taken at any time during the validity of your pass and in any order (or even not at all). Also they can include multiple trains, both in your home country and beyond as long as the last journey is scheduled to depart by 23.59 CET.

For example you could travel from Northern Holland to Amsterdam, then connect with an AMS to Brussels train then take the E* to London (either next day or the same day). That would count as your outbound journey. Only if you use your pass for a journey/day entirely in your own country would you need to pay to leave Holland. (this tends to be used by travellers who may be travelling via ferry or plane to get to the port/airport)

Similarly on the return you can use one day of your pass to get you home from anywhere in the continent as long as it is completed in a single day.

You would only need a paid for ticket to come out of the Netherlands if you used your pass the previous day to travel from home to a station within the Netherlands.

It wouldn’t need to be a “ghost” station, merely the cheapest ticket to the nearest Belgian station on your route, from where you can freely now use your Global pass for your onward journey.

If your paid for ticket is for the beginning of a through train into  Belgium (e.g. Brussels), you simply need to put the same train into your pass from the station your paid ticket ends. There is no need to physically leave the train, just make sure you add the second half before you reach the changeover station.

If it is a train that requires a reservation you may need to get an extra reservation to complement the one you got for the paid ticket.

Hierboven staat theorie-die je eigenlijk al hebt

Voor de harde praktijk zijn gewon duidelijke gegevens nodig, anders blijft het een vaag verhaal. OOK of je toch al korting bij tante NS hebt. En het verhaal gaat gewoon NIET op voor Thalys, €*, en de NJ via DE naar AT. Dat betekent gewoon biljet kopen tot 1e echte halte van die trein over de grens-wat vaak betekent dat je beter een gewoon biljet hele rit kan kopen ipv van allerlei gedoe met 3-4 versch. papieren.

Overigens doe ik dat zelf volop (vorig jaar 8 korte trips van 5-6 dgn in 2 maand-maar met daarbij weekendvrij is dat prima te combineren en spotgoedkoop).