Not sure you can insure a car which is yours under someone else's name. I used to do it in SA but ASAIK, they have to be the same person here (to beat exactly what you trying to do
Putting you on as a named driver will also not afford any [real] savings. We tried this with my sister-in-law and her car. She was 18 though.
I doubt you will get insurance without a valid UK licence. I had to convert mine (South African) to a UK one before anyone would insure me. SA and UK have a swap agreement so no test was needed (phew). The problem with that is then the insurance companies do not give a hoot about anything prior to the Valid From date on your UK licence. I've been driving (legally) since I was 18. According to the UK insurance chaps, I've been driving since two years ago. They could not care less.
Elephant said they did consider the prior licence but when I got a quote without stating it, the value was a few pounds different so it did not afford a huge saving.
Also, don't rely on your dad's no claim bonus / been driving for 20 years as they want proof of a no claims bonus.
The quotes you got, where they for you or for your dad and you as a driver?
I've also heard of (maybe wives tales?) of insurance refusing a claim when it's clear that you were the main driver and the insured driver is only doing you a favour.