Do the people in Reniassance festivals occurring in Britain also speak with faked British accents, or do they use faked French/Italian accents instead?
I'd imagine they fake an American accent. Maybe Burbank, CA?
You can find any number of re-enactment events/groups across the UK from Romans to Vikings to the Sealed Knot to WW2. For most of those Medieval festivals, especially the ones celebrating an event or place (second and fourth links - the first and fourth aren't relevant to this), it tends to be a more touristy event rather than one visitors would get dressed up and involved in (until recently with the US influence).
Definitely this, until apparently the one you've just linked, they didn't exist in the American sense here. The closest you would get here before was out of work actors adding a bit of flavour to some otherwise-a-bit-dull landmarks or historically important places. And even then that wasn't super common.
I always saw the American style as basically a medieval themed Butlins experience. Pure entertainment rather than something ostensibly intended to be educational.
That's it, the earlier ones were awfully dull and worthy and the Ren Fair influence has made it more fun, with visitors now encouraged to dress up and get involved. I wasn't joking when I described them as Medieval cosplay.
It's a bit like how British comic conventions became Comic Cons - back in the day they were a few drafty halls in some relic of the Industrial Revolution or musty spaces in run-down hotels. Now they are Nerdvana, colliding with the old memorabilia shows of yesteryear where you could get a handful of old Doctors to sign something for a few quid and now have to throw a nought on the end of that. If you are lucky you'll still find some actual comics tucked away in a side room where they won't embarrass the starts of that sci-fi show that was slightly popular for a couple of years in the mid-80s.
Is this 'renaissance fair' branding is a new thing? I did a few historical/fantasy weekend larps when I was younger but they were never called 'renaissance fairs'.
Renaissance Faires are a more casual event versus LARPs. It's usually for families. Some people do dress up but it's not expected. Usually you just go for a few hours, watch a joust, do some shopping, and eat a turkey leg.
I think larps are slightly different I would say https://loxwoodjoust.co.uk/immersive-festival/ where the visitors see the reenactors, and while some cosplay, the renenactment is a performance by a cast.
Where as LARP (e.g. Empire) is all the "visitors" are in the cast
I've never heard of a renaissance fair over here. And one of the examples you give, jorvik viking festival, is surely set several centurias before the renaissance.
They ended up called Renaissance Fairs because a radio ad exec in California thought it was a more broadly appealing name when the first one was held, and it stuck.
I watched a catapult fire projectiles into a castle moat outside of Cardiff at a medieval fair. Also got propositioned by a Welsh girl, but couldn’t understand what she was saying.
Renaissance fairs are an American thing. They don’t exist in the UK.
I don't know the UK, so I might be wrong, but it's not an US only thing (beside the naming).
I've seen various form of medieval markets/festivals on several continental Europe countries, and I don't see why it wouldn't cross the channel. Even though, Historical re-enactment is a niche hobby, it's not that uncommon to find group focused on the a given historical period caring a lot about the details, no matter if they re-enact the Viking, The crusade, or Napoleon's army (If you visit Belgium during the Waterloo battle anniversary, you can see these groups re-enacting the battle). LARP is also a thing in the whole western Europe, it's way less realistic as we do have elves and orcs, the biggest worldwide runs in Germany Trailer and UK has also some big ones and a lot of smaller ones.
While not a renaissance fair exactly, there is a jousting tournament in Leeds Castle in Kent once or twice a year. It's a lot of fun with armour, swords, horses, the whole shebang.