As a minimum 40 litres per goldfish. So thats 1 x 1000 litres, or 10 x 100 litres. Really you should be 120 litre for 1 goldfish, then an extra 40 litres for each extra goldfish. And that's minimum, that's not going to give much quality of life.
What size aquarium are you getting?
Do you have a garden you could dig a pond?
Keeping 25 goldfish in 100 litres simply isn't healthy, they will be having such a poor quality of life I'd consider culling numbers. Keeping that many fish in anything other than a decent sized pond is going to take up an awful lot of space inside and tens of thousands of £s. And they are just going to continue breeding and make the situation worse and worse. You need to make some difficult decisions. You arent likely to find anyone to take your goldfish in the numbers you are talking.
What size aquarium are you getting?
Do you have a garden you could dig a pond?
Keeping 25 goldfish in 100 litres simply isn't healthy, they will be having such a poor quality of life I'd consider culling numbers. Keeping that many fish in anything other than a decent sized pond is going to take up an awful lot of space inside and tens of thousands of £s. And they are just going to continue breeding and make the situation worse and worse. You need to make some difficult decisions. You arent likely to find anyone to take your goldfish in the numbers you are talking.