Convert open gas fire to cassette / closed pane gas fire

Hi there
We have an open gas fire in our living room. We’re conscious it’s not v energy efficient etc - has anyone converted a gas fire to a closed gas fire? What needs to be done and how much did it cost (I appreciate it needs to be done by a RGII certified fitter etc) thanks!

I wouldn't call it a conversion as such. We had the gas supply disconnected from the fire place years ago, and then straight to solid fuels. No other outlay apart from the engineers cost.

On a side note, although your open fire will be more efficient than a gas fire, it will not be as efficient as a wood burning stove in its place.

What we were thinking of doing though is to do a conversion from open gas fire to closed gas fire. I love a “real” open wood fire but I don’t like the cleaning up!!