[Aragorn]

Go to the 'Network and Sharing Centre' and select 'Manage Wireless Networks'.
Click on your network and right-click 'Properties'
Select 'Connect automatically if this network is in range' and make sure your network is top of the list.
Open the properties of the neighbours Wlan and deselect 'Connect automatically if this network is in range' and select 'Connect to a more preferable network if available'.
Hopefully that should sort it.