Following the Prime Minister’s announcement of a new national lockdown you can view the relevant guidance that has been issued by the government via this link:

https://www.gov.uk/guidance/national-lockdown-stay-at-home

Most pertinent for the construction industry:

Page 2 of the guidance confirms that where in-person attendance is required, and lists construction as one of those work areas, those areas can continue to operate.

Page 22 confirms that builders' merchants can continue to operate and remain open.