You could also think of it like this :
When you'll do it all at once, 150 hours of time building will cost anything between 13-22k (€ or £ ...)
If you have less time building left, you'll be up for a smaller loan.
Computer science sounds like a good idea for studies.
Wanting to save up before paying for training is good. However, you should consider the possibility that once you'll graduate, you might be looking at this differently.
I experienced the same thing, during my studies I thought i would be saving up before paying for my training.
One year after the end of my studies i'm pretty sure i won't be saving up, i'll get a loan or ask mommy/daddy.
Ask the opinion of your FI. They will tell you how much hours they estimate you need before getting your night rating. Flying at least once a month seems like a minimum in your situation (to keep motivation, to slowly build time towards CPL)