Corret, I am a fully qualified motor underwriter.
Your not obliged to carry on but you will probably face a cancelation charge. IF your the main user now on the clio though, the policy may not cover you in a claim anyway, Its known as "Fronting" in the trade where your using your mum to get a better quote.
However, Most companies actually rate on the highest rated driver, not the policy holder
So Get a quote in your name with your mum as a named driver
She will bring the premium down a bit.
Also, There are ways round the cancelation charge, If you simply tell them you have sold the clio, Theres no subject matter to the insurance thus the policy would need to be cancelled pro rata (no canx fee) as the insurer is forcing the cancelation.
Noel is correct, 30 day quote gaurentee!