I went here recently on a Friday evening. We had cocktails, wine and then dinner in the Conservatory. I have to say that the theme isn't quite as prominent as the website leads you to believe BUT that doesn't really detract from the venue's atmosphere and décor etc - both of which are awesome! The cocktails we had were very tasty and well-presented. The bar staff were polite, engaging, helpful and really knew their stuff. The wine list is extensive - we had a bottle of fizz and two bottle of white. Everything went down a treat! It's a shame that you can't book seating in the bar area as this place is so popular that there's never enough! We had to stand the whole time, although there are coat racks and the staff for us to lean on the bar, which helped.
In terms of the dining experience; I can't fault the atmosphere or the food at all. It's unlikely to be the cheapest meal you ever eat but the prices are nevertheless fantastic value for money as (i) the food is delicious and (ii) portion sizes are generous. If I had one slight criticism, it would be that the restaurant service was slow to start with - but it soon picked up. You'll need to book a table to dine because the restaurant is - deservedly - often full to capacity.
Overall, I would highly recommend The Powder Keg Diplomacy and I hope to return again soon (possibly for brunch, which I hear is good).