I have been buying hundreds of visitor passes over years. Keep changing the address and no problems.
We've done a week long trip up the Thames from Richmond up to Henley stopping at campsites along the way and maybe a few pubs
Top tip - even when moored chuck the anchor over the side to stop the youths undoing your mooring lines and we took a padlock and chain as well.
A huge tarpaulin was a big help to wrap kit up but on one day we tied it to the A frame and made a kind of Camel Trophy rib type.
Have a look at this guide - http://www.waterscape.com/media/documents/1784.pdf
Plus don't forget you can now camp at many of the locks rather than walking miles to campsites. There is loads of information available on the Thames here - Environment Agency - River Thames
Campsites, hotels, locks, the Olympics, slipways, moorings etc etc.
PM me if you want any extra info.