Thanks Brucey, sounds like I should be okay, with some precautions when installing (which the bike shop will be doing, not me) and annual maintenance (i.e removing/re-greasing the stem).
BTW is the Campagnolo Record 1" threaded headset an okay choice? It has loose bearings, rather than the sealed cartridge type, but AFAIk does have a grease port, so maintenance should be relatively straightforward. Reviews I've read seem to imply the overall quality is good.
The campag headset is very good indeed, provided it is fitted, adjusted and lubricated correctly. You can easily kill any headset by simply adjusting it too tightly and the better the bearing quality the more likely it is to happen (you don't feel the excessive preload when the bearings are good quality). You get more, larger ball bearings in a traditional headset so they are (for any given size) almost invariably much stronger than ones with cartridge bearings. Because they have fewer places to rattle, they rattle less if the adjustment is set a bit slack, too.
IIRC the campag record headset use balls in a clip that is (unlike cheaper headsets) designed so that you have almost as many balls in the headset as you can fit. There are seals to keep the worst of the crud out and on bike with mudguards fitted they can last, well, indefinitely.
In many recent versions the lower race is populated with 3/16" balls and the upper with 5/32" ones. Older ones (eg NR) used 3/16" balls top and bottom, and have no seals.
If you are on a budget a Tange Levin steel headset is almost as good and is based on the design of the old NR 'pista' headset, thus having 5/32" balls top and bottom and (unlike the campag one) it has seals.
With any headset on a mudguardless bike you can protect the lower race by installing a tiny shield that covers the back of the lower race. This will keep the worst of the crud away from the bearings.
BTW I prefer a conical expander on a quill stem, but hey....
cheers