You can expect to pay between 18 to 30 pounds per hour at most Driving schools. Please don't be fooled by offers promissing multiple lessons for a cheap introductory prices. Many of these offers involve saving some of the lesson time for your driving test. Some schools charge extra for a driving test or for booking lessons on a weekend.
I keep my pricing very simple. It's £50 for the first 5 lessons.
Normal price per lesson is £25 per hour. If you book multiple lessons in advance i do offer further discounts.