Originally Posted by
SK989
That is not really correct.
The OP is arriving from Qatar (non-Schengen) and is transfering to a flight to Great Britain (also non-Schengen). Hence the OP does not have to posses a Schengen visa according to immigrations rules when changing flights at a Schengen airport such as ARN, unless he is a citizen of Afghanistan, Bangladesh, DR Kongo, Etiophia, Eritrea, Ghana, Iraq, Iran, Nigeria, Pakistan, Somalia or Sri Lanka.
As I wrote in my reply: "I'm not 100% sure, but
there may be a possibility of taking a transfer bus from gate F3 before going through immigration, which would be most convenient for you."
I'm not sure if it's possible to take such a transfer bus from the non-Schengen part of the F pier to the non-Schengen part of T2, but I'll check up on this next time I'm at ARN. If that bus does not exist or does not connect those two locations, it means that immigration is the only alternative.