(i'll only include suggestions which are different to which you've already received)
you could use a lion villager and a dragon villager (drago?) to represent england/wales' national animals? roses across the town in red, white and blue would also be a safe bet! the classic town hall and modern station would also be good as that's just what public buildings look like here. then it depends if you want a more "urban britain" or "countryside britain" vibe-
if urban, as britain's in a constant state of building, pile of pipes would be good, as well as streetlamps/round streetlights for bordering roads. other road themed objects like the traffic signal and no-entry sign would also be good! the parabolic antennae (not entirely sure of the spelling!) would additionally be a nice urban addition.
if country-side, there are a ton of pwps that can apply to this setting, as well as a lot of villager houses which look like cottages (have a look at
this guide) a few examples include the windmill, the lighthouse, wisteria trellis (could make an area replicating the idea of a stately manor's garden), water pump (village-y feel), scarecrow (for farmland, use a qr code pattern of some wheat?), water well and bus stop.. the bus stops in new leaf look freakishly like the one outside my house..

metal benches could also be cute, as a park theme, though it's a shame there are no brown wood benches in the game.
good luck!