Up to 12 weeks in total, depending on how quickly the DVLA (aka DVSA) take to respond to the DGT in Spain.
Timescales may vary depending on region, timeframes depend on the current workload of each individual office and how they communicate with the DVLA (DVSA).

Yes, all people looking to exchange their licence, regardless of age or licence validity need to have a medical check done and obtain the certificate prior to exchanging.

No, if you are not a legal resident in Spain, you cannot exchange your licence.

No, you are exchanging your UK licence for an equivalent Spanish one.

Yes, for the moment you are able to use any European licence in the UK if you are on holiday.

No, the DVLA will inform the DGT if you have ordered a copy of your licence or if you are still holding an older licence and the exchange will be delayed until you hand these in.

No, so long as you follow our instructions, especially with the medical, you will be able to keep all of your categories.

No, if you are over 70, the licence exchange fee at the DGT does not apply to you.

No, the fee must be paid by card or online prior to your appointment.

Yes, you will be given paperwork to use in the meantime, this will Only be valid for use in Spain and is generally valid for three months.

We will provide you with a script of things that can come up and what you can respond, if you are confident enough to speak, you can say them. If you are not, you can simply show them.

On the script we provide there is a section for the DGT staff to write down the issue they have encountered, you can then send this to us and we will let you know what the solution is as quickly as possible in order to reduce the delay by as much as possible.

You should exchange your licence within 2 Years of becoming a resident however in light of the UK leaving the European union it is strongly advised to exchange your licence as soon as it is possible, while the process is still straightforward and does not require any retesting.

This is ill-advised, while it is likely that there will be a grace period, nothing is set in stone at the moment. Again, it is advised to change your licence over as soon as possible.