Fork to 1" Headset Problem

I have bought a new fork for a bike I'm building and I'm probably being a bit of a thicko but I'm having a few problems.
It's an old frame with a 30mm ID head tube where the headset fits.
I have a threadless headset for the 1" steerer.
However, the fork is one of these:
http://www.vivalavelo.com/index.php?_a=viewProd&productId=96
At the bottom where the crown race fits, it's too big. The steerer tube itself has a diameter is 25.7mm
This step to the machined surface is 26.0mm
Then the crown race surface steps up again to 27.0mm.

The headset and crown race fit to the 26.0mm surface but not to the 27.0mm, The 27.0mm surface is 7mm high.

Obviously, either the fork is the wrong one or I've got the wrong headset, but I can't tell which from looking into it.
Can anyone help?

1" headsets have 2 different sizes crown race
It's either 26.4mm (most common) or 27.0 mm.

If fork makers use a diameter of 26.4mm, the headsets with a crown race of 27.0 mm can't be used anymore.

So, it WAS (maybe is, but I don't think so), to deliver forks at 27.0mm and that the customer had to machine (e.g. Campagnolo, VAR or similar hand tool) to 26.4mm or leave it as it is.

Maybe it's not so common anymore to deliver forks at 27.0 mm, but in case you have one, the easiest thing to do is go see a dealer who can machine your fork crown. Approx. 5 min work. GBP 15.-= ???
That's the bad point with online shops...
Don't try to hammer it on yourself or try to make it fit with a file or angle grinder.

Thanks for that.

Assuming I passed on the headset (as it hasn't been fitted to the frame yet) would it be possible to buy a new headset that would fit rather than have the fork machined?

Yes, of course, but most head sets have a 26.4mm crown race.
Will be a bit harder to find one.
Maybe if you look for JIS-standard headsets...

If I'm not wrong, especially the cheaper models are available in 27.0 mm.

I just bought a set of those forks of ebay, they came with the crown race.

http://www.sjscycles.co.uk/product-Shimano-Shimano-HP-M563-Fork-Crown-Race-27.0-mm-1-Inch--22.2-15210.htm

£4.99

This crown race fit only Shmn cartridge headsets.
They don't come in threadless versions, or you have to buy a non-Shimano upper part, that converts the treaded into a threadless version. Then, you have a good headset!