I believe the rules allow up to 50% of previous flying experience (ie in your case 12 hours of your 25) to be counted towards the hours requirement of a course. This is entirely at the discretion of the FTO. If they do allow previous experience they will normally reduce the course fees by a pro rata amount, or else allow you extras elsewhere.
However, as already mentioned, this is discretionary and therefore you should negotiate with each FTO to try and get the best deal.
Also, if you are definite about doing an integrated course you should think about not continuing with your PPL and saving the money for later.