I had my flat valued by 4 different agencies and had varying fees quoted to me from 1% of the asking price to 3%! The average seems to be 1.5%.
All are negotiable, and if there are two agencies interested, you can get them to reduce their fees in order to be sole agent marketing this property.
Also a lot of agencies do a sliding scale of fees. e.g. if you are selling your house for �250,000, they can set their rates as follows: they sell for full asking price, then they get 1.5% but if it sells for less than �230,000, then they will take 1%.
Good luck!