Advice with using property agents

Hi all, we are trying to move to the area and looking to rent a 3/4 bed property. Most on Idealista, Kyro, think Spain& other sites advertise loads of properties but only a couple seem to be available, you contact the selling "agent" and that's it, you're either tied into sole agent &what they're offering, they just don't bother answering,cancel viewings last min or landlords want 6months up front(which turned out to be a bank repo!!) 

How difficult is it really to rent, we have to keep travelling 4hrs to viewings (video isn't an option) so any advice would be welcome please