I used a nike+ but didn't really like it as I never found it that accurate. I then measured my runs online on gmap-pedometer. After doing that for a while I then bought a Garmin 305 and I think it's great. Admittedly I don't use all the functions ( I will get round to it one day ) but if I was to choose again I'd go for the Garmin everytime.
Always take running stuff when I go to the Lakes,usually stay in the Keswick area.Lots of places/footpaths to run on and off road without climbing high.Keswick or Coniston would be lovely areas but I'd tend to stay away from the more busy Ambleside or Windemere.lovely views too!