I have a midterm in REF 102 and have absolutely NO idea where it is. Does anybody have an idea?

It is the building with bridges in it.

Go in the doors you'd usually go through to get to Bridges. But instead of turning left and going down the stairs, go straight through the ugly-ish looking double doors ahead (at least they are double doors in my memory, I haven't been there in a year), and you'll be in the place where all the students wait before the midterm. The room you're writing in looks like the Great Hall in Hogwarts =D (kinda, I think, again if memory serves me correctly). There's usually signs and shit pointing towards that room anyway, I think.

Good luck!

If I recall correctly, theres a door before the door you go into bridges, (on the outside?) and you just go forward (I wrote a test in a churchy (?) looking room in there a year ago...

Yep, just go through the door in the refectory and instead of going down the stairs to bridges, go through the door on the main floor and you should be able to see 102 right there.