I go to a local quarry and pick them out, l have my own truck so transport is cheap. If you have them delivered they cost a fortune. We only have a type of limestone in white or 'green' on the island if we need anything different I pop over to dorset for some purbeck or portland. I once got some kentish ragstone which was very nice. look up the quarries in your area and give them a ring.
Sometimes it is profitable to look in on a saturday and have a good look around and take some of their 'rubbish' this is stuff that has flaws but is good enough for the garden when placed, fault down.
If the project is large be prepared to shift a few tons, a 2ft diameter can be 3cw depending on the density. Hire a digger for the day and save your backs.
