The only place in the UK atm where I can find double curtain poles is at IKEA and the closest one is an hour away. I really want them double because it makes all the difference to me. My favourite summer curtains are the extremely cheap "sarita" ones from IKEA. They are not that great as singles but works great with another pair in another color or with any other kind of curtains. I have them in purple and turquoise and I like them together. They worked great in my old plum colored living room.
That will be my next mission I guess. Double double double! Need to find them.