The compact foliage of some hardy geraniums make them desirable to grow as ground cover plants. The newer Geranium pratense Violaceum and Summer Skies have interesting double flowers in purple and rose pink respectively. The variety Laura is a clean white double flower with less robust foliage. Hayloft plants currently offer these varieties in partnership with the Daily Telegraph.
The picture above shows hardy Geranium Rozane Gerwat in full flower. Other blue varieties included in the Telegraph offer are the low growing Sabini-Blue and Jolly Bee and AGM variety. Rather than spend too much money on offers look for friends well stocked gardens and ask for a root or two. I have just cleared out many hardy geraniums from my garden as they were getting too profuse. (Now the compost heap has a profuse overload).
New varieties and introductions like the double geraniums take longer to mature as plants and you will be lucky to find any being given away at the moment.