Some companies have very basic choice of varieties, whereas others have endless different choices.
Some sell Organic seed, some don't.
The Real Seed Catalogue
www.realseeds.co.uk sells non-hybrid and heirloom varieties of good quality seeds grown in Wales (ie not imported from the continent as most seed is these days) which are not expensive. They encourage you to save your own seed from their varieties and seem to be a good, ethical company.
That said, where I live has very specific growing conditions and over the years I have refined my choice down to just a few varieties which I know do well here. I buy from companies I know sell what I want, such as DTBrown, Mr Fothergill, Chase Organics and Thomson and Morgan (but T&M doesn't have any dates on packets), occasionally Marshalls, (but they tend to coat their seeds). I buy by mail order not from shops, as you can't know if seeds for sale in shops are kept under the best conditions.