There's a lot of differentiation in UK primary schools. My dd's Y3 class (age 7) will have children who can read big fat books fluently, right down to dc who are struggling with three words per page.
Similarly with maths, there will be dc who know all their times tables (will have learnt this at home though, rather than at school - it's actually not that hard to teach once they've got the idea) but I'd put good money there are still dc who can't reliably recall addition facts to 20, and possibly to 10.
The UK system is good for dc who are keen and ready to learn and have had a lot of input at home, but can make others feel like failures early on because it takes them a bit longer to get up to speed. There's a good argument to be made for starting a bit later with formal teaching on the basis that the process will then be much faster. They do all catch up, and lots of EU countries have secondary school pupils at higher maths levels than the UK.
Basic maths, like reading and writing, is not a particularly high-order skill - kids with moderate learning difficulties can get the hang of it perfectly well. Dc who are introduced to it later will on the whole just zip through it more quickly. Think of it as a bit like potty training - if dc are ready to be dry at 2.5 on average, you can start at 2.4 and it will take a month. Or you can start at 1.5 and it will take a year to get to the same point, with lots of argument, upset and wet pants along the way.
fret not.