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From DVLA site..
How the Road Traffic (New Drivers) Act 1995 affects you

If you reach six or more penalty points on your driving licence within two years of passing your first driving test, ie during the probationary period, your driving licence will be revoked. The Driver and Vehicle Licensing Agency (DVLA), acting on behalf of the Secretary of State, will automatically revoke your driving licence when notified by a court or fixed penalty office. There is no right of appeal against revocation under the provisions of the act. You may only appeal against the conviction, which led to the revocation of your driving licence through the convicting court.
All valid penalty points will be taken into account when deciding whether six or more points have been accumulated in the two-year probationary period. Penalty points gained prior to the first driving test, which are within the three-year validity period, will also be taken into account. However, these will only come into scope of the Act if you incur further penalty points during the probationary period. Also, penalty points incurred after the probationary period has expired will be taken into account if the offence was committed during the probationary period.

How to regain your full licence

As the Road Traffic (New Drivers) Act 1995 reverts your driving status back to learner, you must follow the same procedures as a first time applicant ie pay the current application fee for a new provisional licence. An exchange fee will also be charged when converting the provisional to full. A full licence cannot be granted to you until you obtain a provisional licence and passed the relevant driving test.
Full entitlement to all categories of vehicle previously held will only be reinstated upon passing a test in any one of the driver's previously held entitlements. A successful test for entitlement to a category of vehicle not previously held will result in a full licence for that category only.