When an airplane is overbooked, you get a free upgrade or compensation. When a hotel has no more rooms in your booked category, you get a free upgrade. When a car hire company has no more cars in your booked category, they will give you one in a category above.
Not so at Aldeia de São Gregorio. We had booked here a 5-people house for 4 nights, from 26 to 30 July 2012, transferred a bank deposit for half of the money, and received a firm confirmation for the booking. We had indicated that we have two babies and a child, which was acknowledged.
Some time later, we received another email saying that Aldeia de São Gregorio had "overbooked" the house for the time we had a reservation for. It suggested to rent instead two smaller houses belonging to the same establishment, and pay an additional EUR 80.
We responded saying that we would accept this, but not pay any extra charge as we had a confirmed booking, and the booking error was solemnly that of Aldeia de São Gregorio (who admit this error). Aldeia de São Gregorio insisted that we pay the extra charge or chose to get our deposit refunded, and the booking cancelled. We chose the second option and cancelled.
Where business people don't stick to their confirmed offers, one better not trust them.
So our advice for travellers who consider booking at Aldeia de São Gregorio is: even if you have a written confirmation, your booking may be altered and you may be asked to pay more. If you don't want to take this risk, go somewhere else.