Here's some notes from a Thames "resident" -
Marine band VHF
There's no requirement to be able to transmit messages. The PLA regulations only require you to keep a listening watch, but then you'll have to borrow a hand held set from somewhere....
Even if you have a portable transceiver you are allowed to use it without having a license / passed the test in an emergency.
The point is that the PLA issue bulletins every hour and they want you to listen to them in case there's a problem.
Direction of travel
Unless you've done it before, it is not a good idea to do the trip downstream, there aer lots of obstructions on the South Bank (moorings for commercial boats, the LondonEye), and navigating if the stream is running give you less control. The approach to Limehouse is awkward for a NB even at slack water as there are trip boats, police and other commercial users who don't obey the speed limit and cause quite considerable wash.
Much better to do it upstream with the tide and you can hug the North Bank where the obstructions are "kinder".
Insurance
Some companies are vague about / prohibit the Thames transit - so check with them first.
Non tidal Thames
The best way to make most of the river, is perversely downstream as you can make progress quicker travelling with the current.
You'll need a Visitor's license - it ain't cheap, but there are discounts if you are going to the IWA National rally. You can get a license at King's or Teddington Locks (depends which way you are going...)
Most folks just use this as a conduit - we did before we were converted (!) It's beautiful, and there are lots of places to stop - provided you don't mind tying to a tree.
The "best" places may charge a fee - Windsor, Cookham, Henley about £5-£6 per night.
Avoid Maidenhead - £8 and just under the railway!
There are a few EA owned sites and they are free - unless they are by the locks where a fee will be charged.
The bucket-and-chuckit facilities may be yuk (are they really ??) but the self pumpouts at Molesey, Boveney, Shiplake, Mapledurham (new), Abingdon, Eynsham (and two others), work well and run for 12 minutes - good for boats with two tanks.
Water - few and far between is via hydrants (large hoses) at Molesey, Chertsey, Boveney, Shiplake, Mapledurham, Cleeve, Abingdon, Eynsham.
Publications
The PLA used to do a great booklet, but that's been replaced by a map (not so good) here http://www.pla.co.uk/pdfs/maritime/NEW_Inner_PRINT_FINAL.pdf
BW have good publications - already discussed, and the Environment Agency - have a look at everything on www.visitthames.co.uk
I've said enough for now.