In my youth I was there a few times (grew up in Germany). Very nice landscape and friendly people. Before and after the races the course is open for the public. Many got hurt while imitating Randy Mamola, Barry Sheene and Kenny Roberts. Most bike fans around 50 remember these names well...
The course is brutal and unforgiving. Many jumps and high speed tiny turns. As a tourist you can rent a BMW in London and drive over there. A ferry get you to the island. Stay in a Bed-and-Breakfast or camp out and watch the races from your tent.
(now some real good memories coming up)
If you have a chance to see that - go ahead and do it, you will not regret it.
...and if this video give you some goose bumps, you need to go!
Isle of Man TT 2007 - YouTube