Hi OP!
So your 14mo olds will start school the September after they turn 4 (in the previous November) - so by my calculations they were born in Nov 2022 and so will start school Sept 2027? When they are rising five.
You will need to apply for a place in reception which is also known as foundation stage 2 (FS1 is the nursery year that can precede it but is not compulsory - tho I would advise it if possible.). The application will be made in the school year before they start - applications open in (I think) October and deadline is end of January, so this will be Oct 2026-Jan 2027.
Reception is followed by year 1 then year 2, and so on until year 6 - final year of primary or junior school.
You can start to think about primary places now of course - many children attend their closest primary or infant school (primary is 4-11, infant is 4-7, followed by a separate junior school). You will get the chance to express a preference on the application form, anything from 3 to 6 options depending on your local authority.
It's a good idea when it comes around to applying to include one "banker" - a school you are sure to get into (usually your nearest) as the "preference" is just that, not a guarantee. LA has to offer a school place, but if there is no space at any of the schools on your list, they offer a place at a school with spaces - usually a less popular one, hence the advice to put a banker on the list.
IME tbh the vast majority of primary and infant schools are pleasant places where chldren do well, especially if they have supportive parents.
be aware btw that if you are still in UK (btw I am assuimg England - system is different in Scotland and Wales) when your twins turn 11, you will need to have applied for a secondary school place by the end of the October immediately before that (ie when they are 10 and in year 6) to start the September following, at age 11.