Interlaced output is actually a pretty standard capability - the old micros never did it, but that was more due to not having enough pixel-pushing capability (due to lack of RAM) to justify it. For a long time SVGA cards and monitors would use interlaced mode for the very highest resolutions they supported - which invariably looked crap due to field misalignment and so on, but there you go. I would hope that most TVs have better field alignment than that.
Based on tests I've just done on my old BBC Micro and an even older miniature video monitor that I dug out of my spares pile, 640x480 is a perfectly viable resolution for PAL standard - just don't expect to be able to see every single pixel. You'll need to use some font a bit bigger and clearer than Flyspeck 6 to code in, but an 80x40 terminal (using 8x12 characters, which are actually *smaller* than standard CGA) should be perfectly readable and usable if you pick the right font.
That gives you more editing room than a standard VT100 series dumb terminal.
Depending on the TV, you could even go wider or slightly taller, but VGA resolution seems to be a good default. Let people tweak it afterwards if they like.
The key to knowledge is not to rely on people to teach you it.