When budgeting for a PPL, you should always budget for the worst case scenario and not assume you will be able to get things cheaper or be able to borrow something.
If you budget low for the PPL and get 3/4 of the way through it and then run out of money, not only is that money wasted but when you decide to start up again in the future you will be re-learning some of it. Also, never assume 45 hours for a PPL. Where I learnt there were probably 20 or 30 students that I met up with regularly and not one of those students completed it in 45 hours. One or 2 of them are still on-going now.
When I started my PPL I budgeted on the fact it would take me 70 hours because I had read that that was sort of the upper end of the average. It took me 58 hours but to be honest, I probably could have knocked about 5 hours or so off of that but I had lots of lessons cancelled due to weather so I just did some circuits to keep in practise because I couldn't do what I was supposed to do.
Going to a club or training school that is slightly cheaper does not always save you money. I could have gone to another school and got an hour in a 152 for £130 instead of £155. But it would have cost me about £15 each way in travel and sometimes I would have had to stay up there costing me more money in accommodation so I would not have really been saving.
I actually missed one cost off my previous costs and that was ground exams which at the time was £20 per exam.
Borrow what you can but always be sure it is going to be available when you need it. In the UK, there are going to be times when you cannot fly and things get cancelled so if you are going to borrow an aircraft you will need to make sure it's available when you need it and maybe at short notice.
It is very normal for a club or school to charge a yearly membership fee. All the clubs I have approached charged some sort of fee.
Also, watch for added extras. I had fuel surcharge but didn't have to pay landing fees. A lot of places you have to pay landing fees and when you are practising circuits, that can amount to quite a bit.