Whilst I have no doubt that the Property Litigation Association's web site is very interesting, you may find www.portoflondon.co.uk
more useful in this case
The other site that Alan alluded to is Tideway and you'll find that at www.thames-tideway.co.uk
It could do with updating in places, and if anyone has specific up to date information about the tidal thames the webmaster would be very interested to hear . . .
You can launch at any point on the non-tidal Thames without a licence, but the lock keepers check every time you do through a lock which restricts your range rather. You can get day licences from the Envirinment Agency (I think you have to aply in writing to their Caversham offices), or from Teddington Lock. I don't know what safety requirements are enforced on visiting boats.
As you are in Walton, I would suggest that you drive a few miles down to Petersham (near Richmond) and launch there. It's free, and no licence is required. The launch site is at the end of River Lane and is a small beach -- it might be worth checking it out before you turn up with the boat as I haven't been there for quite a while!
From there you can cruise up to Teddington, or down as far as Richmond without having to worry about locks or tides. I recommend the White Swan at Twickenham where you can beach your RIB right outside! Alternatively pick a big spring tide at high water (conveniently at about lunchtime), and go to Richmond where you'll be able to drive your boat right round carelessly parked cars!
Ther river here is semi tidal, and maintained at or above half tide by the lock/weir at Richmond. If you want to go further down river then it's best to time it so that you go out and return past Richmond between HW +/- 2 hours to avoid using the lock.
Just a few thoughts