I would like to plant a tree to obscure my neighbours house - the only
problem is this would put it 6 foot from both our houses - is it
likely the roots would cause problems eventually? I was thinking of
sometiing like a silver birch.

Could a (very large) bush be planted instead without root problems? I
would guess it would need to be 12foot or more to be much use.

PS I do get along with my neighbour just I'd prefer to look at a tree
than a brick wall.