Has the guidelines changed? If one person in the family gets a test, dont they all need to self isolate until the results come through?

[ssd]

One family member has had a test

Other family member has been told they can still come to work, although the results aren't in yet

Is this correct?

Who has told them that?

So family member having test is having test due to symptoms? If so absolutely family to isolate until result.

Thanks, I knew it was wrong

if you have been in conctact with someone with symptons, you mustself isolate.
So if a family member you live with has symptoms and therefore has a test, the whole family must self isolate.
If test result is negative, you are free, if it is positive, you remain self isolating.

We went through this before Christmas. DS was possibly exposed at school and was sent home to isolate. After a few days isolation we all got tested at a test centre that offered it for people without symptoms.
We were all negative except DS who was positive but with no symptoms at all. The rules had said that we could all go about our business and only DS needed to isolate until the tests came back (as per exposure rules from days before) because no one had symptoms.

DH's work tried to discipline him for attending work while waiting for a result but found that, as we already knew, it was perfectly fine. He also reminded them that he had no cause to suspect Covid and as such, could have perfectly legally not had DS tested and still continued coming to work and where would we all be then?

As you say OP, if you are awaiting test results due to someone in the house having symptoms or even if they just have symptoms and you've not tested, the whole house is required by law to stay at home and isolate.

Just awaiting test results without symptoms (ie carers who get tested weekly etc) means you can still go out.