Hi Safe +
The new IET CoP will hopefully clarify some of the above as the HSE are one of the contributors. I will raise the points you make at the next review meeting. Don't aplogise for the cynicism - if the guidance is not clear it's best raised now rather than after the CoP has gone to print.
BS EN 62638 wont add a lot of clarity because its a generic guide on how to perform electrical inspection and testing. It was written as an IEC standard, then becomes an EN and then BS. The IEC rules are that we had to make it generic as it's an international standard. For example, I included suggested retest periods but these had to be removed as they are a UK requirement and other countries have different national requirements. Hopefully having BS status will give it a bit more clout but we will still need additional guidance on our UK regulations.
One of the challenges when producing guidance is the fact that it is purely guidance and not mandatory - where you want to say "you must" or "you shall" you have to write "you may.....you should"
The IET CoP does apply to both plug connected and permanently connected appliances but I can see that some clarification is needed in terms of what is part of the fixed installation and what is an appliance.
Perhaps it will all become crystal clear when we get to the 23rd editon of the CoP....