Dave Poole writes
Kay, I'm not aware of JI type composts that have a peat substitute,
but must quickly add that I haven't looked. As for the Sciarid fly
question, they are most attracted to composts with very high humus
contents and peat based or peat-substitute soil-less composts will
attract them. They also seem to attract Vine weevil more readily than
soil-based.

OK, thanks. So far I haven't had a problem with vine weevil (I don't
grow things in the greenhouse that they particularly go for). I have had
a sciarid fly problem this year, so am having a JI break, but will go
back to New Horizon once I'm over it. I get good results with it, and I
mix it with my own compost for big things.

--
Kay