Last Trading Post sell only aquatic plants; Mike is a very responsible retailer, to the point where even in his shop, he will only stock fish suitable for the average home aquaria and even prefers to buy in home bred fish. Well worth supporting, in my opinion.. say hi from me, if you get his plants.
A lot of other retailers do sell non-aquatic plants as aquatic.
I ordered 50 plants, 2 bulbs for Indian water lily and 3 moss balls - all together I've spent £13 on plants (plus around £4 p+p).
I reckon at my LFS that lot would have cost me £40-£50 so I'd definitely say go for it!