It's a 'how long is a piece of string' question and some Mumsnetters have very long pieces of string.
But of course you can get away for a few days on £1000, you just have to eliminate the parts of the holiday which bump up the cost to leave as much of the budget remaining so you can get accommodation, travel to get there and some for activities/food and drink.
You've probably missed the boat for cheap flights, they need to be booked early if you need to go in the school holidays, but in the future, you could try that for next year.
You don't need to go for a full week/fortnight, a few days away is still a holiday. Cheapest accommodation is probably self catering so you can store and prepare food, to avoid expensive eating out. This doesn't have to be miserable, you can get easy supermarket food, use Too Good to Go, have some takeaways, street food, Greggs etc.
You could book a city centre apartment and go to free museums, city parks, that sort of thing. Going somewhere fairly close to where you live will obviously cut the cost of getting there.
Just because many people spend thousands on holidays because they book a naice cottage in Cornwall and eat out in Gastropubs or 5* AI for two weeks, doesn't mean that everyone's holidays cost that much.