i used divorce-online.co.uk - partly because i knew they were based in my town (i don't know anyone who works there!). Absolutely no dramas apart from my case chap disappearing (unexpectedly early, apparently) on paternity leave! Is more than a one man band so another person took over my case pretty seamlessly.
Did the job admirably. They have several "packages" to choose from (god doesn't it sound clinical!) but i only needed a basic one as i didn't expect (or get) any dispute (we'd been separated for years, just never got around to it. Was first thing i did when discovered i was pregnant though! )
Chickened out of doing it myself as legal wording is a very precise dark art (and the courts can reject it if wrong). HTH