The Thames is 215 miles long with 47 locks. Officially navigable for 126 miles from Inglesham Round-house to the sea (tidal section starts at Teddington Lock), the river is actually navigable for canoes up to Cricklade (a further 10.5 miles). Above Inglesham can be shallow and weedy and is best done in the Spring.
A Thames licence is required for canoes (and the lock keepers will ask to see it if it's not displayed) but this is covered within the BCU membership - make sure you display the sticker on the canoe - don't just use the card in your wallet. All 47 locks are manned and the lock keepers are happy for canoes to use the locks under their instruction so the need for portaging is minimal.
Image produced from the Ordnance Survey Get-a-map service. Image reproduced with kind permission of Ordnance Survey and Ordnance Survey of Northern Ireland.
A table of distances for locks and campsites is attached as Thames distances.pdf
The Environment Agency have an excellent booklet Go Camping on the River Thames. In addition there is now camping at Mapledurham House,
Mapledurham Trust (SU 669 766)
The Estate Office, Mapledurham, Reading, Berks, RG4 7TR
Tel: 0118 9723350 or 07721 094 862
Season: All year
iGreens.org.uk have an excellent mile by mile guide. (If you experience difficulty try this alternative)