Okay, worked out what was happening.
Thought I was getting two copies of the message to the client. Tried a totally different email address and then found that the BCC is being sent to this but the recipient address is still showing as the client's.
I am almost finished and have to say the challenge to learn something new has been both frustrating and enjoyable. Is this normal? :)
Last thing is the order no. I would like this to be displayed on the success page and the emails but for the life of me I can't find it within the variables so I imagine it is generated within the code.
How would I add this to the page and how do I prefix the order numbers in general with a text string such as "ABC000" so the whole thing is then shown on the page, in emails and stored in the database as ABC0001, ABC0002 etc?