Normally there is a 14 day period in which you would not be able to sell the property. After that you would not be able to sell the property for 6 months to a person or persons which were introduced to you by any of the estate agents. However, after the 14 days notice, if someone was to approach you who had not dealt with any of the estate agents then you have the right to sell it to them.
In your case I would clarify the situation with regards using another EA within 6 months.
I have just bought my parents house who took it off the market and the EAs said that as long as it wasnt sold within 14 days there would be no charge. However, I was able to buy it within 6 months because neither EA had introduced me to the property.