They're all different. I've found nurseries that accept funding and vouchers only do so during term time, and if you pay out of pocket it's mandatory to be all year around. Just need to research different places and ask all the right questions because unfortunately I've found some nurseries will withhold information to suit themselves
Some nurseries accept children for term time only and others don't. If you do not want your child to attend nursery during school holidays, you need to find one which accepts that. My nursery for example only accepts that on the preschoolers. For the rest of the nursery they allow you to have summer off but not the other holidays. It is common to spread the cost evenly throughout the year but I told mine I wanted to pay each month the days she attended. So when there's school holidays I pat more that month, but I find it easier to calculate (as they have made mistakes before)
You'd have to find a local authority that is only open in term time if you only want to send during term time. SOME allow the choice but I think they're few and far between. You don't lose the hours they're just stretched. They cater for the majority that need the hours all year round and not just term time. Ours stretch over every month except August and August cost us double and we had to put money away for it months in advance. You'd also have to find one that not only accept no stretching but allow you to pause their space while they're not attending throughout every half term and holiday and not charge you. Unless you go Local Authority like mentioned but they only open 9-3 usually