Hi Paul,
I'm a Portuguese national so I think I'm able to give you some valid recommendations although I don't know the kind of places that please you most.
Not far from Lisbon you should not miss Sintra (
http://en.wikipedia.org/wiki/Sintra). In Sintra visit the Pena's Palace and Quinta da Regaleira (take the guided tour because the place is full of hidden secrets) and in the centre of the town go to Piriquita (a café) and ask for Queijadas de Sintra (a delicious local pastry). If you have the time visit also the Castelo dos Mouros (Moors Castle), Seteais (a five stars hotel in an antique palace) and Monserrate (a big park with a very romantic palace inside). You won't regret to do it all.
On the way to (O)Porto please take a detour to Óbidos (
http://en.wikipedia.org/wiki/Óbidos,_Portugal). Another beautiful and romantic place full of history and almost frozen in time (except for the turistic part).
In Lisbon and (O)Porto get a good travel guide and choose what you like. I think that Michelin guides are very accurate on the ratings.
We are a small country but have an amazing gastronomy and excellent wines (don't think on the French ones, try ours). So, spend lavishly on our delicious food and wine. You also won't regret.
If you need something more specific please feel free to ask.
I wish you a great time in Portugal!