Well that's great, and I hope it does work for you! There is a huge wealth of experience amongst the posters on this forum and they are a great source of knowledge and advice that you'll be able to tap into. 250kts is a regular poster and he recently set up a sea safari type operation out of Poole. He's been going two years now and things seem to be going well I believe.
I did some skippering work for a sea safari company in Plymouth during 2010. They have since stopped running things as they were struggling to get the business. I learnt from that, that marketing is SO key to success!!
At the end of the day as long as you've done you're research and you're realistic with yourself, then you give yourself the best possible chance of success.
I'm very local to Chichester, it's absolutely lovely down there