Since you're looking for stability, I gather you won't be looking for anything thinner than 195 width, so your options are

195/50/16
205/40/17

Bear in mind the Saga has tiny wheel wells, so the above sizes may cause you to scrub the mudguard (I changed to to 195/55/15 and I'm already scrubbing the mudguards occasionally when steering is fully turned).

The size will also affect the speedo readings and for the 205 width you may need to use spacers to avoid scrubbing the inside of the wheel well.