I was watching 'how i made my millions' the other night... an oldish program it was the one with the couple from Ashford who own 500 odd houses. (normal house not odd houses).
They said in the beginning before they were wealthy they bought, waited for increase in value, remortgaged then bought again with the money from the remortgage... and later the wife bought about twenty houses in one day because there was an interest rate cut.
like i said it was a bit of an old program but for it was good (but not necessarily true of course) to here the old man say at the end of the program 'and don't listen to that nonsense you read in the papers about house prices.. theres only one way they are going and that is up'