So, I have decided to wallpaper one wall of my kitchen. As this room obviously gets warm, is there anything particular I need to do to ensure it stays put. I am also after advice on how to spruce up an old terrace house without it being too expensive
Do a scratch coat on the wall the paper is going on. So, scratch marks in the wall (not too deep) is a criss cross fashion with a DIY pallet knife. You could also comsider applying a weak PVA and water solution to the wall and letting it dry before putting the paper on for extra grip. Don't skimp with wall paper, buy high quality and do not buy Laura Ashley. Its thin and stretches. Good wall paper is thick. You don't want thin stuff in the kitchen. Also, if any of the wall paper is perpendicular to worktops, consider putting a glass or high quality perspex splashback over the top.
On your more general query, spend money on the things that matter. Good quality wall papers, buy trade gloss paint (it does not yellow anywhere near as fast as brands designed for the DIYer). Dunhelm Mill does good quality yet cheap curtains, fabrics etc. Ebay is your friend. Go for luxurious touches like decent taps or and/or chrome fittings like sockets and make your furnishings a little cheaper. Hth