If you don't want them to spread too much, make sure they don't set seed. However, this may also stop you getting new and different colours - they hybridize like nothing on earth and the results can be spectacular.
There are specially bred ornamental ones too. I have Nora Barlow in my garden, which is a very different flower shape - you could mistake it for a seed head of some kind if it wasn't so pink!
Check out the Touchwood Seed website for other amazing varieties. What has happened to that amazing plantswoman is so sad - she holds a huge collection of aquilegias (the national collection, in fact), but they have got downy mildew and she has lost hundreds of plants. I cannot even imagine how heartbreaking that must be.