Upvote:1
It is not at all clear what is meant by a old style British driving license
.
This answer assumes an EU style is meant. Any of the older versions (like the Red Book style) would probably not be accepted.
It is also not clear if you will be visiting or if you are a Spanish resident.
Important is only if, based on your status, you are allowed to drive (and not where the car is registered).
If you are a UK resident (i.e. visiting Spain):
If you are a Spanish resident
You should make this application during 2020 to avoid having to take Spanish drivers test.
This can be done electronicly (see Step 1 and 2 in 'Driving in Spain'). The process must be completed by the end of June 2021.
Sources: