The flight from Cumbernauld over the mountains to Oban is magnificent, though you'll need a nice day and high cloudbase. Ditto for most highlands flying. Up the Great Glen to Inverness is pretty fantastic too, though might be a bit too exciting in a strong wind. Plockton has a fairly short runway; do your sums carefully if you're going in with passengers and lots of fuel, and bear in mind getting in doesn't mean you can get out. Mull is supposed to be beautiful, not been there. Heading south, down to Carlisle is a nice trip.
I'm not one for doing any other rating or qualification immediately after getting your PPL; have some fun first, and learn to make your own decisions and generally get some experience. With winter coming along, you might find that means you're often just flying locally for the sake of getting airborne. I got my PPL at this time of year, and by the following spring felt like I hadn't done much. Then came my first real summer of flying, and I went anywhere and everywhere, and it was great. When you get tired of that, then is the time to think about other ratings.
On how much to do as a low hours pilot, my rule, even now, is to only do one new or challenging thing per flight. Either go to a new airfield OR take up a passenger who hasn't flown before OR fly in slightly challenging weather OR do a longer than normal flight. Don't try to do all those things at once. Stretching yourself a bit is good, overload isn't.
