Autoreisen are a well recommended company. I have used them once or twice. V easy to use. The office is in the arrivals by the baggage carousels. Cars all outside in numbered bays.
Avoid Goldcar. And Plus car.
New rules RE UK driving licence. Your paper counterpart is now useless. You need to register online for a code just before you go away. Thiscode allows the rental company to check that you aren't disqualified etc.
After a hideous experience with Goldcar in Pisa one year, I now also use Autoreisen every time we go to Tenerife. They're great - quality of cars are a bit dented and scratched, but all cosmetic and they never try to falsely charge for damages. Usually you can get booster seats free as well, and a second driver. We generally pay around 100 euros per week for a small car. Their costs are reasonable and no dearer than any other reputable company - usually a bit cheaper than Hertz etc.