i went in a suit for my stage 1 tests (stage 2 soon!!)
will be going in a suit for stage 2 as well, even though it says smart casual.
i've got a travel suit, which is very comfy, looks good and puts me in the right frame of mind.
I'd rather look smarter than necessary, than scruffier than expected.
plus, as Pat42 says, its easy to just take your tie off and shove it in your ppocket if you need to...
-A