The Trinity Speed Gem 2 series motors are excellent, and all have features dual ball-bearings and adjustable timing (better ask someone else about adj. timing, as I'm pretty new to the hobby.) Anyhow, they have a 17-turn Sapphire motor in the range, and probably a 15 or 16 turn one as well. They offer excellent performance at around £20-30.
You can find out more about them at www.teamtrinity.com
Hope this helped!
Oblivion