hiring a plane and flying into the likes of Edinburgh and Glasgow to get some experiance flying in controlled and busy Airspace ?
Good idea. I would recommend taking an instructor with you who knows the procedures to assist as your workload could be quite high if you're not used to flying from a busy airport but, having been shown once, you should be able to manage again!
If you're hour building to CPL, try not to get into the habit of using GPS and hone your heading-hold skills. Practice saying ALL your checks out loud (especially if you have a passenger) and practice them twice as often as you normally would!
Cheers
Whirls