If you are a British citizen residing in Spain (regardless of whether you have Spanish residence or not) for more than 6 months a year, then you would need a Spanish driving licence. The 31st of January 2020 will be the official date of the UK’s departure from the EU. If as of this date you do not have a Spanish driving licence, you may drive in Spain with a British permit for additional 9 months. From this date on, the same traffic conditions would apply to British citizens as to the rest of the world. That is, you would only be able to drive with your national permit during the first 6 months from the date of entry or from the date of obtaining your Spanish residence. If you wish to continue driving in Spain beyond this established period, then you will have to obtain a Spanish driving permit from scratch. That is, attending the lessons and passing all the exams IN SPANISH.