I am new to Selenium for Python and was trying to locate element in multiple iframes. This is the DOM element I can see.
As per the HTML you have shared to retrieve the id of the body tag of the second child you can use the following code :
# Switch to the first iframe
WebDriverWait(driver, 10).until(EC.frame_to_be_available_and_switch_to_it((By.XPATH,"//iframe[@src='BuyFlow.aspx']")))
# Fill in Address and ZipCode inputbox and submit form
address_input.send_keys(address)
postcode_input.send_keys(postcode)
postcode_input.send_keys(Keys.RETURN)
# Check Available - Inner iframe
WebDriverWait(driver, 10).until(EC.frame_to_be_available_and_switch_to_it((By.ID,"CreativeLiftFrame")))
print(WebDriverWait(driver, 10).until(EC.presence_of_element_located((By.TAG_NAME, 'body'))).get_attribute("id"))