difficult. The corsas are very special when the weather is right and they have been warmed up, but are very un-special when it's not. I've had plenty of instances (outside of the cold months) where the tyres weren't warm enough and I had a moment. They need heat to grip and town/motorway doesn't generate it, even in the summer. If you only do fast driving then it may be worth the ball-ache of switching tyres twice a year, but if not I'd switch the out for something more flexible. Whatever you do, don't be tempted to stretch out the corsas for much longer.
Yep, I'm considering going down your route.
Like you say, the Corsas are ace when warmed up but lethal when cold (even when the weather is mild). Example yesterday: Stuck in a traffic jam for 10 minutes so the tyres are cold. Got to the traffic lights eventually and "booted it" (not even half throttle) off the roundabout onto the dual carriageway. Cue massive tail out moment as it changed up from 1st to 2nd until the computer reined it in. Luckily, I was in Dynamic mode. If I'd been in RACE mode I would have been in the hedgerow crying.