Patrick: //There was no question of gazumping (which is a moral issue not a legal one) as we had stated that we would consider a higher, or full, offer this week once and if a second viewing could be had.//
You say you were informed by the Estate Agent that, when you requested a second viewing with the possibility of upping your offer, that the Agent informed you the seller had already accepted an offer. that is perfectly normal. If the shoe was on the other foot, and you had had your offer accepted, and the Agent then showed the property someone else, with a view to putting in a higher offer than you, you would be furious, I'm sure.