I've not been to Firecrest, so can't comment on their school.
I'm flying with Falcon at the moment. Great set of instructors, very knowledgable. The aircraft that I've been in (just the Avgas PA28s) are slightly tired but work fine. Fleet is PA28, DA40, Rockwell Commander and SR20. I'll be training on the DA40 soon, and currently doing my night qualification.
At Elstree, night flying training is only performed on Tuesday and Wednesday evenings and the schools have to arrange fire cover etc.
Depending on where you live in Herts, you could also give Stapleford a go, or North London Flying School in Welwyn GC.