Gardening brochures that sell plants are a bit like estate agents' blurbs. You have to treat them with a pinch of salt!
Not sure whether you are thinking of veg or ornamental plants, but you are probably better off googling your aspect/soil type and looking for plants that you like, and then checking them up individually for planting times. As a rule, though, most ornamental plants can go in during summer/autumn, annuals are sown April/May, spring bulbs tend to go in Sept/Oct, trees during the winter. Veg is a world more complicated, and you're best off buying an allotment book with a planting chart to give you guidance.
I think looking through gardening brochures is an excellent idea when you start to plan a garden. they give you an idea of what a plant look likes, its name, conditions tolerated and eventual height and spread.
Parkers, T&M, Spaldings and Van Meuwan come to,mind.
You can make a list of suitable plants, then Google for more info, as naturally the catalogue will show the plant at its very best.
Be aware that plants supplied are often much smaller than they appear, and that things in plant catalogues are often in the "bargain section" for a reason.