The garden centres will shortly have many plants for sale but if you wait until August time there will be lots to buy as bulbs (tubers) of every variety which will be a lot cheaper than plants.

to get the more unusual ones go to plant fairs they are oftena treasure trove. In the past I have bought some lovely ones from Andrew Ward's nursery at Norwell Nurseries Newark. He has a website and offers about 15 for sale.
I have bought tubers in the past and have had varying success. I had 10 dens canis and only 2 grew. the other 8 just failed.

Many thanks for your reply Jimmythe one I will keep my eye on the GC and buy a few if they are available to get me going. I will have a look at Norwells Nurseries as you suggest Sbg and buy some of the unusual ones.

If you soil is on the heavy side, mix some coarse grit or sharp sand in with the soil beneath to prevent rotting off of the tubers.

Thanks Jimmytheone, fortunately I have a very light free draining soil so should be okay.

I can also recommend Pottertons Nursery - they have a good selection of bulbs which they send out in early autumn

Thanks Andrewr I have bookmarked them and will be placing an order when they open in April.

If you can attend an alpine garden society show in your area Pottertons and other traders will be there. There is a show in April. The traders will bring your selection of plants to the show and save you postage and you will be able to see what they have to offer. Check the shows out on this link
https://www.alpinegardensociety.net/shows-events/kent-2019/

Have you already got aquilegias? If not I was thinking they are a plant that grows in similar outdoor conditions but could be started indoors from fairly inexpensive seed now. There's a nice range of colours, etc. & if you have too many they're a good swap item at local meetings