I already get KLM extras for having Flying Blue Platinum status. The extra Flying Blue Miles for being in Business rather than Economy is very small. As I said, the benefit is getting 30 XP rather than 10 XP for the LHR-AMS and AMS-LHR flights. Being in Business Class does avoid getting a middle seat (let's not go into the details of the seat types) since it is not possible to select seats on the KLM flights for this ticket at either MF or KL websites.
The query is: how can I see the seat selection and check the cabin sub-booking codes in Priceline - I cannot see how this?