Andrew,
Hi and welcome to the madness that is Barbel fishing it takes over your life slowly but surely .
You are in prime area Staines is known for some barbel but you will have to work for them so as below....
River Thames behind Homebase and up towards Runnymede used to hold a few barbel but the reports have been sketchy to say the least recently, check out the Thames Thread on the main forum. Obviously if you go further downstream you come to laleham and then onto chertsy mead's both areas hold barbel but are heavily fished mainly by the bivvy brigade.Dont forget you can get the train to hampton court and that opens up a lot more river to you for local info on this area try the TAC lads they have a up todate report of the river downstream from you all the way the the sea.
River Colne, I don't know the name of the area where you goto to get to the river all i know is that it's the housing estate at the top of Staines near the water treatment works this little river is full of fish regular reports of chub and barbel coming out to various tatics but i have heard its a roving river the fish do move around.
Hope this helps and don't forget that Davis Tackle in staines are good guys and they will give you all the help and advice you might need in fact the wil point you to a few fish.
Oh and when you find em shusshhhhhhh
Andy