Thanks again for your reply, I appreciate this.
This is a WordPress.com site that I have not (as far as I am aware) installed any software onto my own computer for (for example, I cannot find any .php files on my hard drive).
The actual site is here:
I believe now that's why there's no Editor under my Appearance. The motive for all this is to restore my stats function, which were working fine from the time I created the blog for three days, then stopped. I started with the Twenty Ten theme, under which the stats worked fine. The stats stopped when I tried out a couple of other themes (e.g. Twenty Eleven) and then reactivated Twenty Ten.
I have also tried to solve the issue by deactivating all the Widgets, but without success.
Many thanks, Rob