Before getting into overall cost it's worth saying that the 45 hours minimum is really just that, minimum. You are likely to need more flying if you have little or no flying experience, have long breaks between lessons or have any difficulty with any of the lessons. 'They' say the average is 50-55 hours.
Most schools base the course cost on their dual rate £ x 45 hours. If you pay 1/3 or 1/2 up front you should expect to get a 'Student Pack' - books, headset, map, checklist, pens, flight computer, ground exam fees etc - all the things you need to complete the PPL.
Other than any additional flying time you also will need to pay for;
A Class 2 medical with an AME costs between £140 - £170 and a good idea to get this before you part with any money.
The Skills test - at least 2 hours of flying at the solo hire rate + around £130 for the examiner.
Your licence application - £168 to the CAA when you have passed.
Landing fees during your navigational training and your QXC - these can be from £8.50 and £40 or more at larger airfields.
Total cost can be between £8,000 and £9,000 for an average student.
Hope this helps, good luck if you decided to go for it!!