To follow on, since I am unable to get a KeyServer to confirm the key I decided to continue (based on the assumption that the Maemo Hackers PUB KEY is correct) and to export the key from gpg and add it to the list of trusted keys for apt with apt-key:

#gpg --armor --export 5FD45CD3EA68E29D | apt-key add -

[Note this is the full key, i.e. not truncated to the last 8 digits – advice on the correct format varies]

The response to the command is;

gpg: WARNING: nothing exported
gpg: no valid OpenPGP data found

So, that is it. I appear to be stuck.