If you do more miles in the car than your dad then YOU are the main driver and need a policy in your name to be legal.
Insurance companys are not stupid.
Also if you bought the car and your the registered keeper then you are simply asking for trouble if you try any insurance fronting scams. Same if you keep the car near your uni and live a considerable distance from uni as you will be screwed by the growing ANPR system which insurance companys DO have access to for crime prevention purposes - insurance fraud being a crime.
Information sharing is more widespread than you think!!!
Just accept the fact that as a new driver you are statistically a bloody liability and hence you have to pay for it!!! You need to build noclaims bonus eventually!
It does seem odd that its so much cheaper for you to go on your dads policy than on your own.
My first car was a 57 plate Mazda 2. A £10,500 car.
For me to be insured on my own policy, 3rd party, was £1300.
For me to be added to my dads policy if he took it out on my car as 3rd party, would add just over £1800 to his policy.
if it helps, you are better of building up your NCB as soon as you can as you will have to pay huge insurance costs sooner or later for your first few years
bear in mind - a lot of these special non stand no claims stuff companies offer are usually of limited use with OTHER insurers.
Even if you are legitimately NOT the main driver, insurers will heavily investigate when a named driver claims on the insurance. As well as this, you won't be building up NCB so your insurance will not get significantly cheaper as you get older.