There is the 490 that goes from Richmond to T5. It is quite easy to change at Hatton Cross where you can get a 490 or (I think) 482. Hatton Cross is in the Heathrow freeflow so there is no need to pay for the jouney.
If I was coming from Kingston I would probably get the x26 and change at Hatton Cross.
To the south of T5 there is the 441 which runs to Staines and Englefield Green via Stanwell. There is the 60 to Slough, 71 to Windsor and the 77/78 towards Slough and destinations that way, there is also the 482 towards Hounslow.
Changing at Hatton Cross there is also the 555/556/557 which cover most of the Weybridge, Shepperton, Walton, Byfleet areas of Surrey.