Royal Decree, approved today, March 1st 2019, containing a Contingy Plan in case the UK exits the EU without a deal on March 29th this year.
With regards to Driving Licences it says that Spain will continue to recognise the validity of British licences and will provide a 9 month grace period for those UK nationals living as residents here, to renew or exchange (canje) their licences for Spanish ones. Check out the Brexit Protocol on how to make use of this grace period.
Of course, the ´2 year resident protocol´ remains in force as well, so if for instance you registered as resident in May 2017 and your licence is subject to renewal under the protocol, you need to renew after 2 years of residency, so in May 2019, and not wait till November as you risk being fined then.
INFO ON 2 YEAR RESIDENT PROTOCOL AND HOW TO RENEW OR EXCHANGE DRIVING LICENCE
After the 9 months, British licences will be subject to the regulations for ´third countries´ and it will no longer be possible to renew or exchange your British licence for a Spanish one, unless a bilaterial agreement between the UK and Spain is in place by then.
For non-residents, so visitors to Spain, this information will be relevant in case the UK leaves the EU without a deal, post the exit date.