That point is a little bit moot since the Norman Civilization can emerge from Greece, for example. Emerging from a Celtic Antiquity Civ such as Gaul is at least a little bit more justifiable, especially since the Normans also fill in for the medieval French, who are a direct descendant of the Gauls via the way of the Franks and the Gallo-Romans.
Ideally we get a separate Celtic path, but the cross-pollination between paths based on geographic proximity (such as Celtic/British/French) is just how the system has been designed to work from the get-go. It is what it is, best we accept that, rather than run in the same "Actually, Historically Speaking" circles like pedantic hamsters.
Moreover because the Normans already represent England, and Castile is the more iconic colonization and naval Civ anyway. Spain over England is the correct choice, if overseas expansion is the niche they were going for.
The Normans on their end, are an excellent choice for a romantic, chivalrous castle-and-knights Civ. (probably the second best after the Franks proper). The only quibble I have is that they're not the best-suited representation of the industrious and mercantile English, but that's what modern Great Britain is for.
Two stages (Normans + Great Britain) is definitely enough for now. Tudor representation is better left by adding a leader from that Era (Elizabeth, Henry VIII, Drake, Shakespeare) while the devs focus on filling in gaps and niches elsewhere. Mods are going to fill up that gap eventually for those that care.
I'm expecting to see Elizabeth down the line, maybe even in the first major expansion alongside Alexander and Gandhi.