We've just been doing the same - a total renovation project - and brought [or wished we had!] the following from the UK for reasons of choice or cost:
Paint -- can be 3 times the price for the SAME product (like Dulux Magic £19.00 in UK, 72 euros here), particularly outdoor paint or 'metal' paint. Wallpaper likewise --- and a very limited choice here.
Tiles, light fittings -- choice and price. If you want a rangecooker they are double the price here (or more) for the same product. Small electricals, like kettle or toaster etc all much more expensive here, but the larger items like washing machines are very similarly priced.
I would also bring bedding as there's more choice in the UK and I think it's a bit cheaper. And you can't get UK sized pillows here (the 80 x 50cm size).....closest here is 70 x 50.
Otherwise my UK shopping list consists largely of stuff you can't get here: good teabags, spice mixes, red lentils, barley, oatcakes, ham stock cubes, horseradish sauce, haggis (yes, I come from up there), dried porcini mushrooms, rice and pasta in bulk bags (just so much of a saving), porridge oats, meusli, paella rice, seeds for breadmaking, lemsips, mango chutney, big bottles of soy sauce, green tabasco, oyster sauce, golden syrup, dark marmalade, kippers, mixed crackers for cheese, dry sherry and marsala for cooking, Pimms, Tanqueray gin (NOT for cooking!).
All the best, Kate