£5k will probably get you a respectable IKEA kitchen, someone to fit it and some cheap flooring. If you hunt around you can find deals and discounts on-line for flooring. If you make sure you get a decent fitter then IKEA can look good. If the fitter's not particularly bothered then the whole thing can look cheap and tired pretty quickly.
If you're looking to redesign the kitchen (ie. move appliances around) then the extra electric, plumbing work will bump it up. You'll probably need to spend a minimum of £10k for a decent finish.
Have you thought about worktops and splashbacks?
Will your current appliances look shabby against the new shiny kitchen? Or are they all integrated so you can hide them behind doors?
Three years ago we spent about £8k on an Ikea kitchen, new appliances (most off eBay), granite worktop, glass splashback and bespoke doors. But our mate fitted it (who is now my DH's business partner) so we saved a lot of money that way. It was part of a new extension we were building so that doesn't include any of the wiring and plumbing.
My DH now runs a design, supply and fit company for bespoke kitchens. Most of his clients spend a minimum of £15k, that's for the cabinets, appliances, worktops and splashbacks, and fitting.