My advice: get the planning permission sorted out before you begin your Meccano project...
...which reminds me of the guy who was in dispute with Croydon Council Planning department during the 1990's after he put the 14 foot-long Marlin that he had caught up on his roof. I always wondered how the roof could take the weight of the thing. When he was told he had to take it down he instead, doubled down and placed a 25-tonne tank to stand guard in his front garden. I would deliberately drive past his house in St Oswald’s Road, Norbury, just to see what he would put out next. There was military hardware, netting, barbed wire and defused land mines, with plans for a Spitfire and an inflatable Winston Churchill. Then it all suddenly stopped after a year or so.