There is not much you can do about gazumping, but a few points can help you minimize the risk. Check out
this help article at www.home.co.uk.
1.Help speed up the sale – the faster it is, the less opportunity there is for the seller to pull out.
2.Choose a seller whose agent has a policy on gazumping, if at all possible. Some agents insist that the seller signs an agreement to turn down any offers after one has been accepted.
3.Keep in regular contact with the seller's agent - tell them when you have completed the survey and received a formal mortgage offer. This way they can be sure that the sale is progressing and are less likely to be tempted to consider any other offers.
4.Make a pre-contract deposit agreement. This involves both parties paying a deposit of 1.5% of the agreed purchase price to a stakeholder, and signing an agreement saying that contracts will be exchanged within four weeks. If one side withdraws from the sale, the other party receives both deposits. If you are a gazumped buyer you therefore get some compensation. This is not a water-tight agreement as either party can pull out if they are willing to lose the deposit, but it definitely reduces the risk.
5.Draw up an exclusivity agreement with the seller after your offer has been accepted. In return for a fee, this gives you exclusive rights to the house as long as contracts are exchanged within a certain period. Few people make such an agreement as it involves hiring a solicitor, but it is worth considering.
6.Take out insurance cover to protect you if your deal falls through. This is yet another expense, but you might be glad of it if things do go wrong.
7.Insist that the house be taken off the market once your offer has been accepted. Check that the board outside the house has a 'sold' sign on it, and contact the agent if it does not.