Isolation question

[Wednesdayafternoon]

So I'm lost with the isolating guidance.
I was of the understanding that your isolation starts on either the day of a positive test or first day of symptoms, however, a lot of people are now saying they're experiencing a cold for a few days before their test turns positive which is normally when they start to improve. So for example, I've had a cold for 3 days. All my tests have been negative but if I tested positive tomorrow would I have to isolate for ten days from tomorrow or from when I started to feel unwell?
This is (hopefully) hypothetical questions! I'm just very confused.

The day after you had a symptom on the list of symptoms I think. But you don't have to isolate at all now.

You don’t have to isolate with cp, d&v, measles or any other contagious disease either but you’re a dick if you don’t.

Yes I agree

The day after your first symptom is day 1. Isolation can now end on day 6 providing you do not have a high temperature.

The 5 day isolation is still guidance / recommended- just not law