I am having the same problem. Sky channels use a teletext subtitle and it is way too big on the screen. I had a customized windows zoom applied and changed it back to normal. This helped a little bit but the subtitles are still too big. I am surprised more sky uk users haven't experienced this or is there a work around I have missed?
Hmm. I never experienced any issues in the past when using Windows 7 and font size set to 100%. Currently I'm using Windows 8.1 and MP 1.6 and have set the font size in Windows to "Larger". I think I'll have to do some more tests. Just to make sure, if you watch the same channel using a regular set top box or directly in TV without MP/computer the font size is of the "right" size?
It is not possible to use 100% on a 60" TV can't see it at all, I have set it to 125% but just too large. Of course the size is right with the subtitle from TV directly.
But I have a TV without antenna so have to use MP.