Full guidance is available by clicking the link below:
https://www.gov.uk/government/publications/covid-19-stay-at-home-guidance/stay-at-home-guidance-for-households-with-possible-coronavirus-covid-19-infection

The main changes are as follows:

LFD tests can be taken in 2 ways:
An assisted test is where the person takes the test themselves under the supervision of a trained operator, and this operator processes the test, reads and reports the result.

A home (self-reported) test is where a person takes the test themselves and reads and reports their own result.

If your assisted LFD test result is positive
If your LFD test was an assisted test, you must self-isolate immediately. You could be fined if you do not do this. You may be entitled to a one-off payment of £500 through the NHS Test and Trace Support Payment scheme if you are required to self-isolate.
You should also take a follow-up PCR test as soon as possible and within 2 days of the positive LFD test at the latest.
While waiting for your follow-up PCR test result you and your household members should follow this guidance. If you receive a negative follow-up PCR test result, and this PCR test was taken within 2 days of the positive LFD test, you and your household can stop self-isolating. However, you and your household must continue to self-isolate if:

• this PCR test result is positive
• you choose not to take a follow-up PCR test
• your follow-up PCR test was taken more than 2 days after the positive LFD test result

It is important to book your follow-up PCR test as soon as you can following your positive LFD test result.

If your home (self-reported) LFD test result is positive
If your LFD test was taken at home (self-reported), you should self-isolate immediately. You and your household members should follow all this guidance. You should also arrange to have a follow-up PCR test as soon as possible. If the follow-up PCR test result is negative, you and your household contacts can stop self-isolating.