Try Adrian Flux or Flux Direct. They will provide learner only insurance. Both my twins had insurance with them as learners. Em got fully comp with me as named driver on her Gran’s old Fiesta for £350.
Now she’s passed, Em pays £1700 comprehensive with black box, which rewards good driving with refunded premium every quarter, up to 20% of the premium. That’s with Ingenie.
James has a Jimny, £2000 for up to 10k miles. Good driving rewards with extra insured miles. Tesco Bank Black Box insurance.
Both black box systems provide regular updates on driving behaviour which they can log into and see their progress. The boxes ensure they stick to the speed limits religiously, and the Ingenie policy makes specific references to braking and cornering.
So no penalties unless they drive like cocks.
There’s also a safety aspect. If the black box detects a collision it generates a phone call to a nominated phone.