In reply to Mountain Llama:
Fair enough. The spending a great deal is not helpful if you want to get rid of wires and have a display in front of you. A cateye RD410DW but it's £80. I've had no problems with my wireless cateye (as long as you keep the display away from LED lights - they interfere badly).
If you want to manage your effort, you might be better off with a heart rate monitor. However, your problem really lies with a wireless display that you can see when you're riding. Happy with a mobile phone in a case on your stem? That might be an option, but by the time you've added up a case, a mount and an HRM you're back to £80 again.
Not easy. Got a Garmin?