Catherine I hope you don't mind me saying this but those mixes look a bit heavy for seeds, even without all the gunge.
I have been using a mix of miracle-gro compost, perlite and seed compost for daylily seeds (the one I use is John Innes but I think that that might be a British brand). You want one that is fine and light, only a quarter to one third of the mix is the miracle gro, I find it just adds a bit more substance for roots to be secure rather that plain seed compost/perlite alone.
I have just remembered that you asked about daylily growers in the UK--sorry, I forgot all about it with the funeral and everything, my apologies.
Ones I have used and recommend are:
"Strictly Dayliles" in Cambridgeshire
"Woottons" in Norfolk
"Pollies Daylilies" (Pollie Maasz is a really nice lady and very helpful)
"A la Carte Daylilies" on the Isle of Wight (their site and catalogue are basic and not updated often but they are very nice and send good plants.)
If I think of any more I will tree-mail.
