As with everything Chris, you cant say never. But Commissioned and Warrant Officers always wore baretha caps, Other Ranks the serge. On occasion, its possible an officer lost or damaged his cap and would make do with a serge Other Ranks version, but it would be an unusual and rare occurance.
If you are talking across the spectrum, in hot climes WAAF other ranks were permitted in the RAF to substutute the WAAF cap with an officers pattern field service cap with appropriate badge. So WAAFs of non-commissioned rank were allowed an officers baretha side cap, but worn with other ranks badge.
I had one of these years ago, very small size, black plastic buttons and slightly smaller than normal, sand cast ORs badge. I thought it was some horrible mish mash until after I got rid of it. Only then did I find out what it was! Although i was only about 15 at the time, we live and learn!