Re flying close to boundaries, I came across a new experience today. When flying along the south coast I made it clear in my initial call that I was going to be keeping clear of controlled airspace (they sounded busy, the small dogleg didn't bother me as I was out for an enjoyable bimble). As I turned over Sandbanks I was told that if I wanted to 'drift in' to CAS they wouldn't have a problem so long as I stayed below 2,000 feet.
In terms of gear used, I'm an iPad user with Runway HD. This has a really useful flight logging tool which gives you the breadcrumbs of your route. Given the above comments about inaccuracy of radar, if accused of breaching this could be a useful defence (always assuming it shows you keeping clear of course !)