When the iPhone pulls its autocorrect it has a bubble that pops up that tells you what word it's going to insert. If you want it tap the "space" bar; if you don't tap the bubble and keep typing. Also, there's a slider immediately above the keyboard provides three autocorrect options. The left one cements in the spelling you want. If auto correct proves really obnoxious you can copy/paste the word.
As an American I don't have a dog in that fight. But even if I did repeated viewings of Yes, Minister and Yes, Prime Minister have jaded me.
Good luck with Mr. Hacker er, Corbyn.