Unless I expect to get seasonings more cheaply at my destination than at home, I load a few small packets of the herbs and spices I use most often into Ziplock bags, plastic bottles or the like. I don't know what the bulk spice scene is like in London. In Eqypt I'd plan to pick them up in the spice market, and have fun doing it, so I wouldn't use valuable luggage space on the way out. I might consider bringing small bottles or bags, empty, to bring some back.
Among the difficult-to-find and expensive items I can imagine you needing would be some modernist ingredients. Are you likely to want, say, xanthan gum while there? A gelling agent? If so, you might also need a small kitchen scale.
I'd bring an instant-read thermometer, and possibly a reliable baker's (oven) thermometer.
A backpacker's camping pan with a folding handle (for compactness) can ensure that you have a reliable pan with a truly nonstick surface, if that's something you value.
I'd consider bringing a silicone lid cover that is heat-resistant, like these Charles Viancin silicone lids
Is parchment paper easy to find there? If not, a roll of parchment paper or a Silpat-style baking liner might be useful.
