my understanding is that private sites being used for private use or for use for the owners business are exempt form planning regs providing that the landing pad is within the curtilage ( ie garden not agricultural or any other use) of a private dwelling. take the fight to them, thieving gypsies.
even if its not private use then the 28 day ruke applies, 25 days obviously not being more than 28 days
noise (antisocial behavior orders) is a different issue and i dont think its been tested re avition before.
sorry have been drinking plenty of strong european beer.
toot toot.