Going to be some unhappy pax diverting to a different country ...
That depends. Long-haul aircraft often divert due to remaining fuel reserves during conditions of fog. The plan then is to do a 'splash and dash', returning to the original planned destination with sufficient reserves to await their turn to make an approach. Of course, if crew go 'out of hours' that changes everything.
Meanwhile, at MAN, holding delays aren't too bad right now. Early to mid-morning is routinely quieter for arrivals on Sat/Sun mornings than we see on weekdays. Also, as often happens when low visibility is forecast / reported, many services operated by DH8D's, ATR's, SB20's etc. remain on the ground at their points of origin until either the weather conditions improve or the operators cancel and consolidate loads with later flights.
Flow control has become extremely adept at managing the rate of short-haul arrivals at busier airports during adverse weather conditions.