Id agree with the others see a Priest.
A friend of mine told me theres a verse somewhere in the bible that your meant to read then leave the bible open on that page somewhere in your house and it wards off evil spirits.
Ask the Priest about that too!!
This may seem far fetched, but so is the thread But maybe an infant died in the house(miscarraige from previous owners?) that the neighbours may not know about or decided not to say anything.
Its not a nice thing to do but maybe your friends could contact the previous owners and tell them whats going on and ask them for any info???
I had the same feeling about my house cos wierd things used to happen, and when my parents "inspected" the house my room was set up with a cot and infant things, throughout all the dealing my parents had with the previous owners my parents never saw a baby!!
[EDIT] Make sure you keep us updated Al, this is fascinating stuff!!