Stick with the current amount of travel, or it will mess up the handling & could snap the frame if you go OTT on travel (10% extra is usually OK)
Look at The Rockshox Tora & Recon forks.
The ones with Motion Control damping are very good, much better than the Turnkey damped ones. (Dart & some Tora's)
U-Turn forks are useful as you can wind the travel down for climbing & then up the travel again for descending
Coil forks are a little plusher straight out the box, but air forks are more adjustable for your weight. Coil forks come with a std weight spring for riders around 11-12stone, you can get lighter or heavier springs for ~£40.
Merlincycles.co.uk, Wiggle & Chainreactioncycles are worth looking at for forks, usually some good deals to be had.