Well I've sorted it (you can stop worrying). My workaround, for anybody cruising Google with the same problem, is to have the emulators display in full screen mode. On the PSP itself this mode means the 4:3 content is stretched horizontally to fill the widescreen display (ew), and if you do this via TV out you get the same stretched image but in a tiny form in the middle of the screen like other PSP games.|
However because the image is already stretched horizontally by the device I can now use my TVs vertical-only zoom to fill my TV screen and get back a 4:3 aspect ratio.
Since PS1 and earlier were all mostly 4:3 this means this system works great as the retro hub I was looking for and has replaced my PC. Good times.
Edited by Psiloc at 18:38:17 22-03-2012
2600, SMS, MD, GEN, 32X, MCD, Saturn, DC, NES, Famicom, SNES, SFC, N64, NGC, Wii, PS1, PS2, PS3, PS4*, Xbox.