Maria, you are welcome and I understand wanting to stay in Lisbon instead of at the Gatwick airport. Lisbon is a wonderful town. We loved it last year when we went. We stayed at the Marriott not too far from the airport. The bus stops right by the hotel and it is pretty easy to get around Lisbon. BTW, we signed up for a Marriott Visa card and got a free night stay. You might check into that. I just don't know of any other cheap way to get to Lisbon. Funchal does not offer a lot of options. I do know that it was about the same to fly from Funchal to Gatwick on BA as it was to fly from Funchal to Lisbon on Portugalia. Good luck!

Editing to add: I also remember Grupo SATA flies that route, so I checked it for the 12th and the fare was 197 Euro.