For the most part, I found Brandarama surveys suck. Some people have a high approval rate, but the most are low.
What I do is clear out my cookies, complete one (by getting to that complete x number of offers below to claim a prize), then do a few other surveys (e.g. myinsiderdeals, winning surveys, etc.,) then try one more Brandarama. And that's the amount I do in a day, no more than two of them - unless I'm feeling lucky (which is always a waste). Also, I have two e-mail accounts that I use for Brandarama. So maybe try an alternate e-mail if you haven't done so already.