If you go down the modular route it "may" save you money but not in the way most would expect. We have all heard about how it can save you money flying but that is not the end of it.
If you get a PPL and then sit the modular ground school once finished you will at least know that you have the Writtens out of the way, not a small task. I have met several people who did intergrated at Oxford and failed the written exams. Unfourtunately the way Oxford structure it by the time you discover that you can not pass these you will already have spent a fair wedge of your funds in Arizona on flying.
Should you fail some of the writtens you can continue with the flying once you have returned to the uk alongside re-sits. Thus enabling Oxford to continue to spend your money. In the last few years I have met two people who tried at Oxford who were doing their IR but still had exams to pass and then failed for the final time thus losing the lot. Some people will never pass the written tests and I have known more than I can count on both hands who have had to give up.
If you are one of these (and I am not suggesting you are) then I think it would be better to find out when all you have spent is the cost of a PPL and ground school than when you are nearly £50,000 poorer.
Just my thoughts on it so please don't all flame me down.