Should I defer my university entry by 2 years to be eligible for 'home' fees?

I just finished my A levels with 5A*. I was about to start my Engineering course at the University of Cambridge, but 3 weeks before my course, my fee status was changed from "home" to "International", which is about £40,000 per annum. Apparently, they made a mistake initially assessing my fee status, I don't meet residency requirements as I've been resident in the UK for a bit over a year. My family doesn't have that kind of money, so I have deferred my entry to 2018 and I will be using the gap year to gain industrial experience, raise funds and apply for scholarships. I will still be an International student next year, however, if a take another year off, I will qualify as a home student in 2019. I will save at least £120,000 during my 4 years if I do that, but I will graduate aged almost 25. Will my age cause problems with employment even though I will have two years of work experience? I would like to have a second set of eyes on my situation. Thanks.