At first I was impressed with what UK2000 had done to London Heathrow. It has a very nice and realistic design and is less than £20. The runway looks very nice, the taxiways are accurate and the gates look brilliant. In my opinion, it is one of the best looking and realistic airport add-ons. However, after a few landings there I realised that there is a major problem with it. It absolutely eats frame rates! This is an add-on that will make most PCs lag like hell. The computer that it was tested on is in no way old and slow. It is decent computer that can easily handle Fly Tampa’s Hong Kong Kai Tak add-on (review below), even with an add-on aircraft. Even using a standard aircraft with UK2000 Heathrow, it is really slow. You can of course fix this by turning down all the graphics but why would you do this? Then this add-on would be near pointless as it would look terrible and so would the aircraft. I have yet to find an add-on for London Heathrow that looks realistic and runs well on most PCs. This is not a problem with all of UK2000 add-on airports but is definitely a problem with their Heathrow add-on.In conclusion, if you have a top of the range PC that can handle anything that comes its way, and you want a Heathrow add-on that is a reasonable price and is realistic, and then by all means get this. But if you are not a serious flight simmer who wants to spend a large quantity of money on a high-end computer, then don’t buy this. It is good value for money, considering money and appearance, but it will ruin the fun at this speed. It is not worth the money in that sense. As it was so slow I ended up having to uninstall it from the computer, as I love flying in to Heathrow smoothly. For the moment the standard Heathrow is just fine for me, but I will continue my search for the best Heathrow add-on, and when I do, I will tell you.