Mine probably cost me around £8-9k over 2 years and about 70 hours (my 1st 14 hours were an RAF flying scholarship, then didn't fly for 8 months so pretty much had to start from scratch).
£5k does sound cheap, and it's about what I was quoted for my training. If you go over the 45 hours, or do more dual than was budgeted for then the cost goes up. Also, you've got to get your medical and pay licence fees, including the radio licence.
If I were you I'd budget for 60 hours at least. Worst case senario, you finish in 45, and you have money left to build some experience. Better than going way over budget, and having to worry about finances half way through the licence.