Well first and foremost, immigrants to the UK are not all alike, so this isn’t going to be a yes or no answer. But you knew that when you asked the question.
I can only speak for the immigrants I know. Firstly my parents, who came off the boat in the late 50s. They were very big fans of the full English, although they saw it as an inferior version of their own traditional breakfast.
Why stop at black pudding when you could have white pudding too! But making soda bread wasn’t practical for a mother of two holding down multiple jobs at once. So I was deprived of the traditional food of my ancestors, the full Irish.
Growing up my mum must have imagined that I was never fed at school because for my entire school life she fed me a bowl of porridge and a full English with a fired slice every day. I think that’s the reason I grew up to be 11-inches taller than her, although I’m slightly wider too.
Even though she’s in her 80s now, I can barely make it through a visit without her forcing a bacon sandwich on me.
Aside from my immigrant parents, I also have an immigrant wife. Honestly, my family is thick with immigrants, one of my mums immigrant sisters even moved here with a Spanish husband. It’s outrageous. Her other sister did go native though, and married a man from Essex. Her brother didn’t just immigrate to London, he wasn’t satisfied until he emigrated again, this time to Australia.
But I digress. Coming from the colonies, I had expected my wife to immigrate with some pancakes and grits or something. But she took to the full English like a raccoon to a picnic. You see, as much as they bang on about bacon in the USA, the vast majority of them haven’t even seen real bacon because they don’t have passports.
Many foolishly think they understand when they hear us describe bacon to them, deciding it’s “Canadian Bacon”. Which is a bit more like gammon than the super-streaky nonsense Americans microwave before putting on a burger. But nothing like traditional English…er…Danish bacon. Wait, more bloody immigrants! Anyway, I prefer we keep our secret from that lot. If they only knew, they would eat the worlds supply in no time.
I have witnessed a German attempt to create an English breakfast. It was a passable attempt, but often they are too health conscious to really revel in it. No sign of a fried slice, and they seem terrified of toasting bread any darker than light beige. Sure burnt toast is full of carcinogens, but who wants to live a longer life at the cost of a really good breakfast.
I did have an anglophile French friend that could almost certainly have done a better job. But most other French people I’ve known have preferred the espresso and cigarette start to the day. That’s probably not still the case, but it used to be.
Italians I suspect wouldn’t touch a full English with a gondola pole, as they are too busy laughing at us for ordering Cappuccino after 11:00 am or feeling physically sick at the though of sweetcorn and pineapple on pizza.
Immigrants of some religious backgrounds must forgo the delights of a full English because it’s not kosher of something. So I doubt they have strong feeling about it.
Anyway, I can confirm that many immigrants eat a full English, despite it being inferior fare compared Jonny foreigners epic full Irish. But I’m sure many immigrants are forced to lower their standards in foreign lands.
Also, many avoid the full English, for reasons of religion, health or good old fashioned disgust. What can I say, not everybody aspires to my less-than-athletic figure. I don’t blame them in the least.
Now to the final part of your question, Brexit, and it’s impact on foreign nationals consumption of bacon, eggs, sausage and more. I don’t have really good peer reviewed datas on that aspect of your enquiry. But I’ll go out on a limb and say nobody who might ever have eaten a full English would ever forgo that delight just because of Brexit. Why on earth would they?
I suspect that the whole movement to leave the EU was to stop the cultural-appropriation that we have suffered over the years. Champagne was invented in London, as was Guinness, Scotch eggs and Cornish pasties. A line had to be drawn.