For all the talk of Brexit, the United Kingdom is one of the most welcoming countries in the world, its edges softened after decades, some would say centuries, of welcoming immigrants onto its shores. The country is also one of the fairest. Most expats find that where they have come from does not mean anything once they are in. The nation's sense of "fair play" meaning you are treated no worse, or better, than anyone else.
Once working in the United Kingdom you will have access to its state schools, its hospitals, its libraries... and to other benefits of a society that embraces both the principles of a free market, and the security net of a behemoth National Health Service simultaneously. That means unlike many other expat destinations, you do not only have 'international' private schools to consider, but can also think about the free government option as well. There are pros and cons to whichever you go for. Government schools can be excellent although always fiscally challenged, the UK's private schools out of this world, along with their (stratospheric) fees.
As an island (well, two islands) it’s fair to say that culturally you'll have lots to explore. Accents change in 30 kilometres, although you'll be forgiven for not being able to pick up those differences for a while, perhaps even years. However there is also lots that unites the kingdom. Without trying to be comprehensive - television, pubs, sport (mainly watching others), whining (the weather, public transport...), incomprehensive foods (sausage rolls, mushy peas), and so it goes on. After a few months in the country you'll have gone native on many of these (the weather in less than a day). Other cultural artifacts will leave you baffled after a decade (mushy peas, I mean... why?)
Your experience of the United Kingdom will however vary enormously depending upon where you live. If you live in London, in many respects you are really living in a global city more akin to New York than Birmingham, the UK's second city. The world calls London home - it is the sixth largest French city by population with 85,900 of its citizens, joined by 123,000 Poles, 254,000 Indians, 108,000 Irish, 77,000 Italians, 53,000 Germans, 48,000 Americans, 23,000 Jamaicans, 93,000 Nigerians, 49,500 Japanese, 30,300 South Africans... we could go on, and on. Try finding someone British waiter or waitress in a shop or restaurant - it's a mission!
With such large expat populations finding a home from home is probably not going to be enormously taxing, something that will not be the case in the UK's more provincial cities and towns - although even here times are changing. Friendliness will not change, but perhaps ease of entry into the community will be harder - as it probably would be in the your own countries outside its largest cities. Be prepared for a longer transition.
How long will of course depend on the community. Expats live across the United Kingdom. In the south west of England life is in general quieter and more rural - think Dorset, or Cornwall. The south east has more of a London spread and claims the same geographical make up as the French Champagne area. The Midlands tends to be dominated by its bigger cities (Birmingham, Warwick Coventry...) but it too has fantastic countryside. The North of England is home of great industrial towns of Manchester, Liverpool, Newcastle, Sunderland, as well as amazing country - think the Yorkshire moors, self-proclaimed Gods country. There's the East of England, dominated really by Cambridge and the countryside of East Anglia. Scotland (beautiful Highlands and lochs, Whisky, Edinburgh, Glasgow) is a whole other country, as is Northern Ireland (now better known as the land of Game of Thrones) and last but not least Wales, in this writer's opinion the most beautiful country in the union, but perhaps, given its very tight-knit communities, the least accessible for expats.
In terms of private schools there is a definite tilt towards the South East which means accessible from London, and its airports. There are however great schools (private and state) across the country so wherever you do end up, WhichSchoolAdvisor.com help will be able to help you identify the right school for your child.