If Freesat were going to make a Windows app it would surely be aimed at Windows phone users, not PC users, as most PC users will have an iOS or Android phone they can use.
I suspect they’re probably not going to spend time/money on developing an app for Windows phones given the market size. Just my opinion.
There were pleas for YouView to develop a web interface for the YouView app almost from launch – always met with a brick wall. Bluestacks reportedly worked though – might work for the OP’s purpose. I’d forgotten about that.