20k miles per year is pretty high! It may make a diesel more sense. The bonus with the I-ctdi civic is that it doesn't have a DPF to clog up. It does however have an egr valve that gets nicely sooted up! The clutch is indeed still a problem, they had a coupe of revisions 305,315 and the lastest being 325 but even that is still known to slip. Honda have however, upped the warranty period on the clutch quite substantially.
Another problem that is just starting to filter through to the I-ctdi is a cracked exhaust manifold (its a two part welded item which splits!). Honda will replace this FOC up to 7 years / 125000 miles. Some have managed to get this done without fhsh so your mileage may vary here!
That's the ticket right there....
The engine is a cracker, and I'd be willing to bet it'll give you thousands of trouble free miles. The lack of any worry over the clutch is a major bonus too.
If you sign up to Civinfo, you get a further 5% off parts at cox motorparts ( A Honda dealer with cracking prices online for oil, filters etc). Honda dealerships aren't particularly cheap for oil etc, but Cox are pretty good.
If you want parking sensors (you may well do) keep an eye on ebay, I got genuine Honda ones for £100 (paid indy £30 to fit). Honda dealerships charge a fortune. Of course you can fit cheaper unbranded ones, but the Honda ones come pre sprayed!
When you pick the car up have a look on the underside edge of the doors. There may be rubber bungs there, if they haven't been removed by a previous owner then remove them. They are counter productive due to the fact that dirt blocks them and then the doors hold water.