Having worked for an estate agent,
I agree with all the above, except, the bit about reducing the the commission if contracts are not exchanged in 3 months. This is NOT down to the estate agents, as James says.
A friend of mine has a sale running, empty flat (leasehold so always takes longer anyway) and 'cash' buyer.
Buyer "I have the cash so I am not having a survey"
Buyer "The searches are back"
Buyer "Everything is on target"
After a month of this my friend (the estate agent) phoned the buyer's solicitor. They had never heard of him.
Turns out that he had instructed another solicitor, but as the sellers solicitor didn't know, the initial contract had been sent to the initial solicitor who had returned it 'not known'.
IN the meantime the sellers had sold their house, bough another and moved.
Summer is a quiet time for viewings, it should pick up when the kids go back to school.
If it doesn't you may be on the market at too high a price. If a 3 bed semi in your area usually goes for £245,000 and yours is on for £260,000 you are too high, especially as that is over the stamp duty threshold.
This is a website which can tell you what the houses in your area actually sold for (not what they were marketed at).
You just have to put in your postcode.
http://www.ourproperty.co.uk/