****Correct link in comments*****
Cheapest for 50ml. Free Click & Collect
If you need home delivery, follow the link by clicking on "get deal" from The Perfume Shop, which costs £31.99.
Alternatively, 100ml gift set can be bought for £38.25 from The Fragrance Shop" using code "gift15" (thanks to Sabiha2013). Check this thread http://www.hotukdeals.com/deals/mens-acqua-di-gio-giftset-tfs-2097697