Actually “racism” in the UK is largely post-1940s. There was a lot of trouble with the US troops stationed in the South before D-Day because black soldiers discovered there was no “colour bar”, and I’ve been told virtually all the US army in the UK had to be confined to barracks. Despite which a number of black soldiers ended up marrying white English women.
Racism really got started once Caribbean immigration started up again (it had been quite extensive into Bristol during the slaver era, and there was a lot of intermarrying) and the far Right tried to stir up trouble - just as they did so successfully in 2015-16.
My father assures me that during the 1940s and 1950s it was all “don’t ask, don’t tell”. Alan Turing got into trouble because, being a bit naive, after his boyfriend stole a load of stuff he called the police. Even that might not have really been a problem if the US wasn’t screaming at the UK about faggots and security risks, and the UK was desperate to keep in with the US on bombs and missiles.
And we didn’t have “interracial couples”. We had Anglo-Indians, we had a few black and white couples. The numbers were small, but the police wouldn’t have been interested.
In the upper reaches of society, anti-Semitism was often correlated with pro-Arabism. It was considered very OK to hang out with the Bedouin, Egyptians, Iraqis, Iranians and so on. Their upper classes really did send their children to school and university in England. Of course anti-Semitism did not apply to the right kind of Jews* like the Rothschilds.
There was a lot wrong with the culture I grew up in; its attitudes to women, outside progressive circles, was often dire; there was a lot of domestic violence, attitudes to foreigners were often xenophobic and the class system was, until the 1960s, pretty rigid. But it’s a mistake to assume that the UK shared US obsessions around “race” and gender, until we were more or less forced to.
*to avoid frequent misunderstandings, this is irony.