I need to sell quickly becuase of a job relocation and am concerned that my current house may take a while to sell because of its value. Is it common or good practice to offer estate agents an additional bonus on top of standard fees to ensure they market your property for a quick (but not too low price) sale ?
If so, what sort of figure or % is considered acceptable ?

Well before offering a financial incentive I would try and establish an amiable personal relationship with the agent - Visit them in person, explain your position and nudge them to make that little extra effort for you. Sounds kinda obvious I know, but you can get a lot more from life in general by simply being nice to folk!

--
Paul
www.InsideTrack.co.uk
Property Investment Education

"may take a while to sell because of its value"

If a property is priced correctly and is marketed properly it will appeal to the right buyer.

If you need to sell quickly you may have to compromise on the asking price.