Need some new tyres for the Mondeo so a set of 225/40/18's

The ones I've got on I love because they are really quiet on the motorway even though they are cheap and cheerful, event wl905's at £45 a corner

But

How much better are the more expensive makes?

The car has done less than 3000 miles in the last 4 years so longevity isn't really an issue, but standing around is and now I've noticed some very small cracks in the tread I don't want to wait to get them replaced, even though the car may spend the next month standing and then get back on the road for ford fair most likely so you can tell I use it as an everyday motor

Don't forget it's running some ap's so even on no grip surfaces the stopping power is absolutely phenomenal, in fact, when I was on the track at ford fair I simply could not brake too late, and out brakes everything, including a 400 brake green focus who overtook me on the straight and then braked while I sailed past him before braking later and I STILL braked too early

I'm also looking at some suspension upgrades in the near future so I want something that will complement the driving experience without making it unfit to go to the shops in or drop the kids off to school tyre wise

Cheers