I hired a double medela symphony when ds was born with a TT and would latch at all. At £45 a month it wasn't cheap but compared to formula, which was our only other option, it was about the same. I also bought a swing from eBay and used the bottles etc I got with the symphony for £45 I mainly used it when we were visiting or somewhere the double wasn't practical. I was just as efficient at getting the milk out, only one boob at a time!
So on your case I would say get the swing of only for the occasional use. If you plan on exclusively expressing hire a hospital grade pump (or see if the hospital loan them out)
If you get a doule pump, for it to work you'll need some sort of hands free device! You can buy expressing bras that the funnels fit through, however, I just bout a cheapo bra from Asda £5 I think an cut a hole for each nipple/funnel to fit through.