I used to have a heavy duty gazzebo that we used at work when valeting cars in the rain, but i had to stop using it as i was paranoid about it flying away in the wind, we had pots filled with concrete initially to hold it down, but then resorted to adding 25kg water barrels on top off them during the windy periods.
I was never happy with it, so i sold it and built one myself out of scaffolding pipes

I paid a local company 110quid to make me up the heaviest duty tarpaulin they could do (they made them for trucks apparently) and had eyelets put in every so often to tie it down, it lasted around 6 months until we got some mega winds, so bad it blew the bloody tree down at the end of the car wash (approx 2 foot trunk so not to weedy) and it just ripped the eyelets out, so i removed it before it killed somebody.
Nowadays i have turned the scaffolding creation into a bomb shelter type arrangement, with a proper metal roof

205 litre barrels filled with concrete now hold it firmly in place