I'll give you the full gen - you can have a loan of it if you want, I'm that evangelical about it.
It's a Nokia N95 :
http://en.wikipedia.org/wiki/Nokia_N95
Most of the big shops will have it now, but it's a new phone so they want a premium.
If you want the handset free, you're going to have to sign up for an 18-month contract.
Different shops will have different deals, but be warned - progressive pricing for data is in its infancy and there are still places which want to charge you so many £ per megabyte of data - which for a 3.5G phone means lunatic costs if you dare download anything!
The best deal I found was T-Mobile who offer 1 GB of data a month for £7.50 (it's called "Web 'n' Walk")
T-Mobile aren't the best for voice coverage. What's inside the phone isn't just for voice calls though :
When you're at home it joins your home wireless network.
The GPS is quite nice. It's a proper unit - that is to say it doesn't rely on any other outside data (wangi might be able to verify this) but it's clever enough to use the web or mobile cell data to find out where it is if it loses sight of enough satellites (again, wangi knows more than me about this!)
I'm sure you'll get a GPS signal in the Pentlands, and much of the rest of the globe.
Nokia Sports Tracker is just one app written for the phone - there will be more which use the raw data in interesting ways. It's free software, and saves a file whenever you tell it you're "training" - in KML, which can be read by another bit of free software called Google Earth.
I've seen nice stuff done by marathon runners who keep all their training data online - you can then browse exactly where they went and when on streetmaps, all online - one minute you're looking at them running near Ocean Terminal then the next map can be a marathon in San Francisco.
As toys go, this one is a knockout.