Hi
I have done mine but it was some time ago
But I hope this is of help .
A gestor can do it for you ,but from memory you
Will have to pay for the medical and at traffico ,
I think the gestor will charge ,100 euros approximately .
The medical is ,50 euros approx and traffico is 23 euros approx .
It is cheaper if you can do it yourself or know someone which I do .
Firstly you have to get an appointment at traffico to
Change your license to Spanish .
At traffico you hand in your UK license ,plus
You have to have two photos of yourself ,plus passport ,
Plus n.i.e.number, and padron they gave me a receipt for the !icense ,
And photo copies of everything .
They will give you a list of medical centers re your medical .
Which if I remember are eyes ,co ordination , general questions
And alertness ,if you pass they will pass on to traffico
I think and they will give you a copy .
When you're license comes back from the UK re points etc
And they have the medical pass , they will contact you via email
To collect your Spanish license
You must have the right size photo ,I would imagine
That a good photographic  shop would know the requirements .
I hope this is of some help .
Good luck
Ps you might need an appointment at  medical center .