An important point to note is that Gatwick Airport is closed for several hours from something like no later than 2200 until 0300 or beyond, and that includes the business lounges. The airport claims never to close because there is (I think) a single café somewhere on landside open through the closing period. If a supermarket claims to be open 24 hours, but you can't buy any milk, fruit, veg, or any groceries at all for many hours daily, and you can't in fact be in the shop without being forced out of it - BUT there is a sweetie machine in the foyer - then you would dispute the 24hr claim. So far as I know, the same applies to every single international airport in the UK with (it has been suggested) the possible exception of some part of Heathrow. The comparison with main international airports abroad is striking.