For me Daleks fit almost entirely 'seriously' within the setting thanks to that excellent Dr Who episode.
British do boffins well, but also are very good for gritty Dog Soldiers type scenarios.
If I were to do 'serious' Weird War British they would be supernatural or anti-supernatural and character based. Priests with anti-supernatural abilities, an unusually lucky private or one with premonitions, hedge wizards or druid, or 'talents' organised under the SOE or similar organisation. Underdogs on patrol, pitted against the horrors of German supernatural engineering, or sent into the flames of Caen to stop the Nazis' own team of talents (similar to the Godlike RPG, more specifically the background comic series published in Dungeon/ Polyhedron and sadly nowhere else).