Pulled it down, now won't go up. Taken the trim off, can't see anything in the way. Would the most likely suspect be the regulator and if so can it be tested with multimeter or other equipment? Is there anything else I should check?

It would most likely be the regulator.
Check the window isn't caught in the guides and that the guides are lubricated, and that the window is sitting in the regulator okay.
But in most cases, the reg is cactus.

Doesn't look like it's caught anywhere but the cable is loose but as far as I can see not broken.

http://s1014.photobucket.com/user/tigerbike1/media/magnacable_zps62bf38ad.jpg.html?filters[user]=137798125&filters[recent]=1&sort=1&o=0

Hope this photo worked but this white plastic thing is the only thing that looks broken.

http://i1014.photobucket.com/albums/af265/tigerbike1/magnacable_zps62bf38ad.jpg?t=1386392380