Last year I got some short stemmed "yellow" anemones that would flower all summer. They turned out to be the common tall pink ones that spread like mad and didn't flower until August. They replaced them this spring and what's coming up looks exactly like what they sent last year. Last year I also bought a blueberry that was about a quarter the size I could have got for a similar price locally.
Parkers are finished as far as I'm concerned. We live and learn.

I find Parkers is always a gamble. They are cheap, but for me only about half their stuff succeeds. I bought some pure white patio dahlias from them once. The flowers opened up bright Barbie pink, a colour I hate.

I agree with Jonah re - 'the gamble'

Because of this I never ever plant Parkers stuff into their final quarters, I alway pot them up and nurse them along, until I deem them suitable for planting out!

True I lose a few, but at there prices, and the discount I get, I find in the end, that they were generally value for money!

I have bought quite a bit from this year infact as I write this, they have sent me an e-mail telling me my latest order has been despatched!

If you look in my photos I just put my results on there today.

As you can see the Freesia are lovely!

Well I'm glad some of the stuff is OK then. It certainly is cheap but its so disappointing to waste a season when stuff doesn't perform.

I've seen so many complaints about Parkers that I never buy from them. To be fair though, Freesias can be fussy little beggars and often don't bother to grow.
Hpefully you started your dahlias off in pots, lightly dampened the compost, and kept them indoors or in a greenhouse, unwatered, until growth started appearing? If you planted them straight outside, I'm not surprised they haven't grown...