I was in your situation when I started out a year ago. I gave up trying to compare costs as it was just too complicated! Quite often the website prices are out of date.
Some include home landing fees, some don't. During circuit training I was doing up to 6 t&g's and one full stop landing in a lesson with less than one hour of flight time, that could be another £60 at some places.
Some charge a/c & instructor seperately and for different durations. Even if you study at home (or in my case on my daily rail commute) for the exams there will be a few lessons that are solely one to one ground briefings with your instructor and no flight. What about R/T training?
Does the school charge a club membership fee?
There are other important things to consider such as;
Is a grass runway prone to waterlogging or does a coastal location get affected by sea mists? The more lessons that get missed because of things like that, the more hours you'll likely need to do.
What about the journey to the airfield? - you'll be making it a lot!
How many instructors do they have? - what happens if your regular one goes sick at short notice, on holiday or onto a commercial training course? What happens when aircraft go for maintenance?
Best thing is to short list a few schools then go and see them, find out how they operate and go with the one that feels right for you - it probably won't be the one with the lowest hourly rate.
And be very very wary before paying a huge sum up front to get a discount. If they go pop, you've lost it!