Travel to Bologna is relatively cheap and the car hire is expensive compared to Portugal. Easyjet is the cheapest by far. I book my car hire with www.economycarhire.com who are the cheapest and fairest but still expensive.
I always stay at Hotel Castello as what is the point of going to visit Senna places without staying at Senna’s last hotel. It’s 150 Euros a night, ask for suite 200 as this is the one Senna stayed in. The hotel is about 30 minutes from Bologna Airport. I strongly advise you to take a sat nav as it makes it a lot easier to get back to the airport. I have never gone back to the airport in six attemps without getting lost.
Imola is a further 30 minutes from Hotel Castello.
The Memorial is easy to find if you look at my page. While at the circuit i can recommend the American Diner as it serves a great meal. Its under the main grandstand.
While in Italy i always try and visit the Ferrari Museum which is about one hour in the opposite direction to Imola.
The other place that is a must is Trattoria Romagnola which was a restaurant Senna always ate at when in Imola. His autographs are still on the wall twenty years later. A word of advice, I ordered the meat and did not realise you had to order vegetables separately. I felt a right knob when the pork chop arrived on its own, They don’t speak very good English and my Italian is crap.