In these cases, most flag carrier airlines do the same price gouging stuff.
The tactic that I got over is to fly an irrelevant carrier such as Lufthansa, Air France, LOT etc... in these cases

While it would not offer the direct convenience as BA non-stop, they wouldn't likely realize the football demand instantly for a connecting itinerary.
For EURO 2024, I have refundable flight tickets for matches of Turkey for example where TK immediately blocked lower RBD's, Air Serbia and LOT were more than happy to sell discounted connecting options maybe within 1-3 hours of the draw.

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Can't give a UK example but back in the days when the Real Madrid - Galatasaray quarter finals in the UCL back in 2013, TK was asking about €1000-1500 round-trip from Istanbul while for the same exact dates, Swiss via Zurich; Lufthansa via Munich, Alitalia via Rome, etc... was available for the €200-250 range. I didn't attend that match but helped someone booking flights.