The Euros will be fine at the stadiums....they will have Olympic style airport security (no expensive scanners though lol). The Olympics it was quick and easy. Provided you didn't turn up last minute!
Same for the last World Cup. You get searched at the fanfests too. A Cambridge Utd friend got turned away from São Paulo fanfest as he had a blowpipe he brought from Manuas in his bag! I imagine blowpipes are banned at Wembley too