I was only refering to marinas on the non-tidal sections, no other option on the tideway obviously. St Kats is £27 min for up to 10m, still cheap for London though. Staying in a marina on the non-tidal sections, seems to defeat the object of boating on the river for me, its all about being self sufficent and not being dependant on power, water etc... and finding all those great quiet spots not normaly accessable.