From the October 1987 (#45) Issue of Crash Magazine:

"FIREFLY BURNS OUT: FIREFLY has been withdrawn. It was a way of creating a mini-Prestel (known as a bulletin board or BB) on your Spectrum with a Beta disk system and a Voyager 7 modem. Firefly was a good piece of software, but it was ridden with bugs and wasn't being updated. This looks like the end of standard BBs on the Spectrum - only Micron is left, and you need special software to access a Micron BB."