Thanks to all who have contributed.? I have a much better understanding of the issues involved here now.
Basically I will avoid using the KC33 and stick to a 12v PSU I also have (although the noise benefits of the KX33 will be missed).
I have certainly noticed high heat levels - particularly when using the high duty-cycle modes like FT4 and FT8.? I have a fan available which is keeping this under control.
Thanks again.
Geoff
G3YTX