One thing we in the UK have in abundance that are rather rarer yon side of the pond are Garden Centres and Nurseries that are not add ons to the harware chains.
Nurseries, run by plantsmen and women, give you the opertunity to browse for less common plants, and even put in an order for propogation if none are available 'off the shelf' of the variety you are seeking. They usually don't sell much more than plants and compost and possibly the more common garden tools.
Garden Centres carry huge stocks of most of the more usual plants, trees and shrubs, but propogated elsewhere and bought in so they tend to be the things in flower at the moment or the latest trend rather than the unusual. However they are also more likely to have the specific plant available now, if they stock it at the time of year. They also have associated cafes and a large range of gardening accessories and associated items, from summerhouses to wellington boots and bird seed, as well as tools and landscaping materials. So they are also a 'day out' just to browse and have lunch. Their staff tend to be quiet knowledgeable too.
Hardware store chains also have a garden section, as in the USA, but the specialist knowledge in the staff is often absent.
Online aquisitions are often disappointing when you don't get to choose your own plant and transport costs are large so it is my least favourite option, however it does open up a lot of options for really rare plants and seeds. I bought Clivia seeds from New Zealand and have had 100% germination both times so that option worked well.
So that is my order of preference for garden shopping, local Nursery, Garden Centre, Hardware Chain, and then Internet and mail order.
