My shot at the Angevin Empire, revolving around the Plantagenet tradition of fierce, strong warrior kings acquiring vast swathes of land by charisma, diplomacy and sheer balls-to-the-wall power.
Angevin Empire.
UA: "Warrior Kings" Units trained in a city celebrating WLTK day receive 5 free xp, and an extra 5xp for every pre-industrial military or defensive building in the city.
UU: "English Longbowman" +1 range, receives double GG points from combat, but takes significantly longer to build.
UU: "Plantagenet King" Replaces Great General, if the PK ends its turn adjacent to an enemy city or unit, the capital will enter WLTKD. If a unit adjacent to the PK captures a city, all cities will enter WLTKD.
Not sure if this is either absurdly OP, or very much UP, either way I think adjustments can be made, I just worried about cluttering the civ with too many bonuses or maluses, for example I considered adding on to the Plantagenet King UU, if killed, all cities enter resistance for the next 2 turns, but that could be too harsh. I was also considering adding, stationing GGs or high-levelled units in a city increases the production of military units/pacifies the city. God, too many potential bonuses.
One thing is that the other UU, the English longbowman, is probably the best fit for an Angevin civ, it gave the entire empire their power, as opposed to the Elizabethan army, which had little land power and had almost entirely phased out the longbow in favour of muskets. If this is becoming a British Isles split, and with the presence of 3 other British civs, it looks like it might, then I'd suggest giving Elizabeth a new unique. I'd go with this:
High Theatre: Replaces Zoo. Provides 2 culture, unlike the zoo, however provides no base happiness. It has a slot for a great work of writing however, which, when filled, provides +3 happiness.