Post online check in - upgrade possible?

Hi All and Happy New Year.
Our next trip is Man - Las on 14th April. If we check in online is it still possible to buy an upgrade at the airport assuming there are any available? We have a miles plus money ticket (X class) - the first time we have used mpm. This seems to have ruled us out from being offered the chance to buy an upgrade online prior to check in. Thanks.

[Neil]

Doing OLCI will not affect your ability to upgrade at the airport if available.

Thanks Neil.