Sunny,
There are no set fees for driving lessons - some private driving instructors tend to charge less for lessons than driving schools. You can expect to pay anything between £18-25 for an hour's worth of tuition. Depending on the area you live in, you can get discount on driving lessons for students, block lessons discount (that is when you book lessons in bulk, 10 hours or more) or introductory discount which is basically the
1st driving lesson free.
The time required to pass your practical driving test really depends on each individual. Some people learn faster than others so there's no one rule of all. As a minimum, you will need to have at least 45 hours worth of lessons and private practice is recommended as well.
Reputable driving schools like BSM and TheAA have facilities for their students such as
practical test simulator and theory test exams which can be done on-site. Some private instructors will also help you with your theory and do mock up tests as well. There are many websites where you can practice the driving theory test as well.