https://www.sentencingcouncil.org.u...riving-where-custodial-sentence-also-imposed/
For offences committed on or after 13 April 2015, where a court imposes a disqualification in addition to a custodial sentence or a detention and training order, the court must extend the disqualification period by one half of the custodial term imposed. This is to take into account the period the offender will spend in custody. This will avoid a driving ban expiring, or being significantly diminished, during the period the offender is in custody (s 30 Criminal Justice and Courts Act, 2015). Periods of time spent on remand or subject to an electronically monitored curfew are ignored.
Where a rehabilitation course is completed, any extension period is disregarded when reducing the ban.
For example where a court imposes a 6 month custodial sentence and a disqualification period of 12 months, the ban will be extended to 15 months. Where a rehabilitation course is completed, the reduction will remain at a maximum of 3 months.
Consult your legal adviser for assistance.