I have been in this situation for more than 9 years now, and I see a lot of confusing remarks in this discussion so far.
The situation is really very simple.
As a director you are automatically also an employee of the company (even if you are not paid a salary, or do not have an employment contract in writing). That is
all that matters to UKBA. On various occasions, when I had to prove I was exercising treaty rights, I have submitted a letter like this:
I declare that mr X has been employed by company Y in the role of director from (start date) until the present day, and is expected to remain in this role for the foreseeable future.
And then let it sign by my co-director (or the company secretary). Never caused me any problems.
You have another hat: shareholder. That enables you to do some tax optimisation by choosing how much to pay as salary and how much as dividend. That's one of the advantages of this construction, but is
irrelevant for immigration purposes.