The lounge at Prague is fairly modern, but for a third party lounge is one of the better ones.

I’ve only been during the mid morning / early lunchtime. There was bacon / boiled eggs / hash brown / cut meats / various cheeses / breads / fruit / freshly popped popcorn (you add your own flavourings) / crisps / fountain soft drinks (Pepsi max etc) / fruit juices / a good bottled beer selection too.

Once through immigration, turn left out of the duty free shop and go up the escalator. Give yourself 15 mins minimum to walk to the gate that BA uses (they’re the furthest from the lounge) and remember that you will have security at the gate just prior to boarding - just in case one of those beer bottles were to fall into your hand baggage that it won’t get on board!