Don't plan on taking cruise type luggage on a Europe LCC. We really messed up last year. Booked EasyJet to get us back to London after a cruise. WELLLL, only one of our bags (out of 7 bags for 4 people) met the requirements. It was something like 40 pds. pp. We ended up throwing away the plane tickets and we all got on the train. The over weight charges were more than the clothes, including some expensive evening gowns. IE Ridiculous. Don't know whether you can buy another seat. I don't think any of us asked.