Las Palmas for definite - and at a very reasonable (by UK standards) price
- we got both via the Seaman's Clinic along with lots of good advice and a prescription for some 'just in case' antibiotics and anti-histamines.
I know I had all the phone
numbers and stuff for them at one time, but must've given them away; sorry. I can advise though that the place you need to be is: Delegación del Gobierno Plaza de la Feria, 24, 35071 Las Palmas de Gran Canaria.
You'll find it on Google
maps and it's no more than a ten or fifteen minute walk from the Las Palmas marina/anchorage; you need to go in the front door of the building (east side) not the door at the rear where there's lots of people queuing.