I wanted to write a word of warning about Rentalcars.com. I booked a car with them in Luxembourg. On the reservation I stated that I'd arrive at 7pm and I added my flight number. My flight actually arrived at 9.30pm so I was a bit later than what I'd stated.
On arrival at the rental company counter - InterRent in this case - I found that it was already closed. Apparently they close at 8pm. For all the other customers, they leave a key with the parking garage attendants and it works just fine. But there was no key for me. Apparently they either thought I was a no show (even though they had my flight number and arrival time) or they did not have enough information about me when they closed (e.g. they didn't have a copy of my voucher from Rentalcars.com).
In any case the result was that I had to rent a car from the friendly chaps at Avis that cost about 3x as much as (Eur 100 vs Eur 30).
When I explained all this very politely to both InterRent and to Rentalcars.com, each one pointed at the other and told me that because of the mismatch between my stated arrival time and the flight number, it was my fault. No refund. No apology. Nothing.
Needless to say I think it's frankly a bit ridiculous to take my money when I haven't even seen let alone driven the rental car and given that they had all the information required to leave me a key. But if they want to lose a customer for life so be it ...
I'm writing this review so you can be forewarned. Think twice before choosing the cheapest option ...