Hi all,
Thanks for your replies!!!
The main reason for me waiting to change flights is because I am a little bit worried about the connection time in CPH. At this point, I have 55 minutes time in CPH, and 2 hours in ARN. If I were to get on the 18.05 flight from ARN, this would give me an additional hour in CPH. Provided that there are no delays, there should be no problems at all with this(55 mins), but a delay of even 20 minutes will mean that I will have to run (at my best ability) to get past passport control etc and onto the PEK flight.
I will check-in the whole way to PEK when I get to TKU airport. I will also ask them if there is room on the earlier flight from ARN to CPH. If not, then I guess I will just go to the gate in ARN and check once I get there

If nothing at all is available, I will just "go with the flow"
Out of curiosity, what would make the 18.05 flight from ARN to CPH "illegal" when the 55 minute CPH-PEK is not ?
Thanks again for your assistance!
Btw, this is the fare rule:
Cancellation/refund after ticket issued: full refund if flights cancelled before departure
Changes after ticket issued: changes permitted for same carrier/route/reservation class