Came back from the trip. In the end we only looked for a specific iPad and compared prices in Carrefour, Sharaf DG, Virgin stores, Jumbo electronics and maybe others I'm forgetting. Everyone had exactly the same price as the Apple store. I'm not particularly good at haggling, but I tried to ask for a lower price and I was ignored; some of the sellers even walked away from me. In any case, Apple prices in the UAE are much better than the UK, so we bought the iPad at full price.