Employment status law is immensely complicated.
The chances are that everything that all potential "employers" will tell you is wrong, and the changes are pretty good that everything the Inland Revenue will tell you is wrong.
The only for-sure way to find out whether an engagement counts as employment or not is to take it through the courts after the event. (Unless it's particularly bang-to-rights fair-cop one way or the other, but yer average punter won't even know that without paying for professional advice.) This is partly why the Inland Revenue won't say for sure in advance - to be honest they don't have a clue either.
As an example of the IR's record of getting these decisions right look at contested IR35 cases: the IR lose a hundred or three for each one they win. So when they tell you "this definitely counts as employment" it's seriously possible that they might be talking complete bollocks.
This is, to put it mildly, an unsatisfactory situation. There are people lobbying for changes to the law to clarify this stuff, basically looking for a "right to be self employed", so that if the worker (under no coercion) and the client both want to regard the relationship as not being employment then they will actually be allowed to. This is, however, oink oink flap flap territory with the present government.
In particular, re:
The IR will take the view that
It doesn't matter a sausage what view the IR take. What matters is the law, as defined by the view the courts take. The IR lose more than they win, so don't believe any view they give you without at least taking further professional advice.
And in this context "professional advice" does
not mean your everyday high street accountant or solicitor: they quite often don't have a clue either, not being experts in this particular field - "professional advice" means an employment status expert.