Both yes and no.
Baggage should not be a problem since all flights are part of one ticket and BA and SK have an interline agreement. The baggage will be tagged to ORK pretty much automatically.
Getting a boarding pass in UME for BA might be a hit or miss.
But do make sure you don't end up with a paper ticket. From SAS sales info page:
Note: BA will
from 01JAN11 not accept
psgrs with
117-paper tkts
Note: SK will
from 10FEB11 not accept
psgrs with
125-paper tkts
(117 is the prefix for SK, 125 is the prefix for BA).