We need to be clearer with this so apologies for the confusion. Calculate the sha256 of the passphrase to get the namecoin private key (in hex form). Then import the pk into namecoind or namecoin-qt with importprivkey.

Thanks for the response mate, I did try this but perhaps I made a mistake with spelling.

For everyones reference however, should we include the spaces when applying the sha256, or should it be one continuous string which we hash.

eg. sha256("police helicopter apple") or sha256("policehelicopterapple")

Include the spaces. Exactly as it appeared.

Thanks for the clarification, though I'm a tiny bit confused.

Using my passphrase, I can successfully generate a sha256 and then import my bitcoin client, which then provides the same bitcoin public address as shown on my profile (I left it as the default on profile creation).

This shows that I have calculated the hash on the correct passphrase (no errors). However when importing the same key into namecoin-qt I'm getting "Invalid private key (code -5)".

Am I doing something fundamentally wrong, the key should be able to be imported into both -qt clients right? One for the ownership of the bitcoin address and the other for ownership and management of the u/name. I'm determined to get my head around this

Edit:

Ok it looks like Armory will happily accept the 64 long private key, but namecoin-qt seems to prefer the 51 long keys. Perhaps in 'wallet import format'. No error anymore, still trying to determine if its worked though.

Yes, when importing the private key into Namecoin-Qt, it needs to be in wallet import format. Make sure it's a Namecoin WIF, though. You might find this library helpful: https://github.com/halfmoonlabs/coinkit.

I imported the address into namecoin-qt but don't see anything under Manage Names and I don't even see a transaction? Do we need to re-index or anything after importing the private key?

Just calculate the sha256 of the passphrase and you'll get your private key for importing.

Is there any way a smart-enough-to-be-dangerous person can choose their own passphrase (e.g. screw themselves with a weak one) with your service?