Did you try TGM's exceptional value plants as you can save a bit with these and they are good too. Postage always adds a lump, but if theres nowhere local with decent plants to buy you have to bite the bullet and pay to get the good stuff. All the other sites mentioned above are good so will be worth doing a checkout comparison as you may well save some money. Its a tricky one as some dont have the range of plants available and it may be specific species you want in which case again you have to pay...its worthwhile planning what you may need in the future too and lumping it all into one order which effectively saves shipping costs.
Cheerio,
Ady.