can named drivers drive other cars third party?

No, only your mum's car.

Generally, the driving other vehicles extension usually just applies to the policyholder. If you want to drive your Dad's car, he would have to add you to his policy as a named driver. Some insurers offer temporary named driver cover, so you could go on for a week or a month etc, rather than pay to be permanently on there.

I have yet to hear of an insurance company that will allow a named driver to drive another vehicle not belonging to them with third party cover only.

You don't own the car so therefore you aren't the registered keeper so you cannot drive another car if you're only the named driver on an insurance. Talk about having you're cake and eat it , you're the named driver on both your mum and dad's cars , are you not happy with that?

Assuming you mean it is mum's policy - no, you cannot - only the policyholder is allowed to drive another car on a third party basis, and only if her certificate of insurance clearly shows this. It is not automatic cover, if it is not on her certificate then she does not have this cover.

No you are not. Only the policyholder, which you are not, may drive another car on third party cover.

No, only the policyholder gets that extra cover (and now come fully comp ones do not include that at all for anyone)

I Agree with Laird, Be Very Careful with this Topic, check the Insurance documents or Give them a ring and clarify.. As if you are not covered and you get pulled You are in Troooooooouble! :)

i think you have to be aged 21 or over to drive a third party vehicle.

I don't think you can.