Agree with all above, I fly in Scotland around Stirling and as that's between Glasgow & Edinburgh airspace you have to keep an eye out for light aircraft traffic.
Couple of other points to note: Definately keep to the right side of roads etc, I know you don't use them at you're stage as you tend to do straight legs, but I've found once I had my PPL I quite often follow roads and things when flying in the local area as it's easier than having to fully plan routes and constantly look at the map. I've also sometimes found myself at fairly low level under low cloud, joy's of flying during a Scotish winter I suppose!! - and everyone else is following the roads as well.
Also I like to pick a random altitude, rather than flying at 2,000' I use 1,700 or something as other people seem to follow 500' increments, it obviously isn't foolproof but it may give you vertical separation uif you visually missed another aircraft.
Telling people where you are is a good plan too, I use Scotish information normally on route but if you hear another aircraft on frequency and you believe he may be near transmit and tell the controllers where you are and your altitude,hopefully he's listening in.
I'm sure we all go through this stage, I certainly did!! - but the 'big sky' theory works pretty well, and with a good scan I doubt you'll get really near anyone else, you certainly don't very often hear people talking about mid-airs and I'm sure you know how much people like to pass on disaster stories!!