Heed IO540's advise, he is absolutely right.
Should you buy an aviation style GPS? In my opinion, yes. It'll have all the maps, airports, directories etc, already loaded, so turn it on, and go. It'll give you distance to destination, ETA (once airborne), your ground speed, what course your flying, what your tracking, how far off course you are, and what course to fly to get back on track, as well your altitude, and current position, and what ever else you set the screen up to display for you. If you can afford it, try a Garmin 295.
One very important caveat, LEARN HOW TO USE IT BEFORE FLYING WITH IT. The last thing you need should things go wrong, is to wrestle with the GPS unit because your not sure how program the next waypoint, or how to find the 'nearest' airport.
Secondly, I don't know about the UK, but in the U.S. you are required to carry current maps for any area you are flying over. My advise: Make a flight plan everytime, draw it out on your maps, and keep them handy. Pay attention to what the GPS is telling you, compare the ground your flying over to your map, and update your position every 15 min or so. Some terrain you might fly over might be quite featureless, no rivers, no roads, no towns for great distances. Pay attention. Maps by the way, are relatively cheap and easily available from any FBO.
Enjoy the friendly skies,
W.B.