When you say WMC doesn't see the tuner Is it showing in the Device manager?
I have heard of a few people having problems with WMC and tuners in x64, and there have been a few patches from windows update including at least one specific to Europe & UK.
Not something I actually use so can't really help with specifics but it could just be that the drivers
are just not ready yet
and you'll have to wait for the certified ones