One of my favourite tricks how to keep whipped cream fluffy and hold its shape even when it’s in room temperature is to stabilise it with a tiny pinch of xanthan gum. I use 1/8 tsp of xanthan gum for 300 ml cream. Always choose a cream with enough fat otherwise it won’t whip. You can get either whipping cream with 36% or double cream with 48%. BBC Good Food has a nice guide about whipping cream.