Second this.

I fly LHR-EDI a couple times a year for work and have found this lounge to be fine. It is next to the gate they normally use for the EDI flights. It’s pretty big but can get crowded at certain times.

There used to be a separate area, like EDI has, that was more selective. I was told it was less crowded and the food was supposedly better. But the last couple times I've been there it has been closed. Not sure if it is permanent or not.

The other BMI lounge, which is nicer, is on the other side of the terminal and is intended for international flights. This is only a guess, but you could have a 15 minute walk to get to the domestic gates.