Have you reviewed your current car insurance, I assume you have it because you must by law in the UK.
See here
"What do I need to do if I want to drive my car in Europe? Every car insurance policy in the UK will provide you with the minimum level of cover that is needed by law to drive in all of mainland Europe. No matter where you are going in Europe, you will be covered - including non-EC countries such as Switzerland and Norway"
Probably why no-one is doing it...
Also read this guide from the AA about what steps you need to take before driving in Europe. Some countries have specific laws in regard to safety (eg France you must carry a high-viz vest, hazard triangle, etc). You also need to make modifications to the vehicle, the headlights for one need to be adjusted so they don't shine into on coming traffic.
Personally, if you do have to get additional insurance - I'd fly and use trains... it'd probably cost you a lot less than the insurance alone. Not only will it be more expensive than your fathers cover (insurance is highest for drivers of your ages no-claims bonus will make a difference) the excess will be very high because of the age of the other drivers.