I had a Rover P6 3500S when I was 21 - it felt like a rocket then, but wouldn't now!
OP, as your car still has run-flat tyres on it you could try replacing them with non-runflats before you start looking at different wheel sizes - especially as your 107 alloys look so good!
If you do look at changing wheels too, with a 3.0i I don't think you can go smaller than 17 inch because of the front brakes.
700 miles in a week seems a lot for a weekend car BTW - maybe your daily is getting rested!
I've not removed a CDV, (I had it done :roll: ) but I believe it's just a case of disconnecting the hose from the CDV, unscrewing the CDV then putting the hose straight into where the CDV was.