When we were part of the EU the Construction Products Regulation (CPR) EU 305/2011 applied - basically if a product was aligned with one of the 444 harmonsied standards published in the Official Journal of the European Union (OJEU) then the product was to carry a conformity assessment CE mark as meeting the essential requirements listed within the standard.

We retained the regulation on departing the EU but now have an equivalent list of designated standards maintained by the Department for Levelling Up, Housing & Communities against which UKCA conformity assessment marking is to be applied.

https://www.gov.uk/guidance/construction-products-regulation-in-great-britain

Unfortunately the change has not been smooth to implement due to limitations with the number and scope of test facilities in the UK so there have been a couple of delays with full adoption of UKCA in construction.

The current target is 1st January 2023 with transitional arrangements regarding existing CE marked goods on the GB market in the interim (separate arrangements exist in Northern Ireland due to the protocol where EU rules are still followed).

Meanwhile the Building Regulations themself have been seeing significant change as the governement adopts various recommendations post Grenfell. The regulations still invoke our retained Construction Products Regulation but move further in adoption of European Norms (test standards) in the supporting Approved Documents for example fire testing where BS 476 is being replaced by EN 13501, they also impose revised requirements such as the fire performance of materials in higher risk buildings.

https://www.gov.uk/government/collections/approved-documents

New additions include Approved Document S: Infrastructure for charging electric vehicles

Not sure CDM 2015 has really kept pace

Just to add to what Roundtuit has posted.

If it is a bespoken designed item then regulation 10 of CDM 2015 will also apply.

I also suspect if there was a fatality linked to the item then the HSE will try and stretch reg 10 to take enforcement action against the "person who commissions it".

Specifying is design so it fall on the designer to specify the product or item correctly. Most specifications require compliance to British Standards, BRE, UKCA etc.​​​​​​​

If a buyer ( normally a QS) goes and buys a product outside the UK, they become the “person who commissions it”. They have to check compliance with the specification. If they alter the specification they become the designer and take on the design liabilities under CDM 2015 . If they fail to do either then they and/or their employer may be held liable.

CDM is concern with the construction process only, except for places of work. For buildings in use, the Building Safety Act will place duties everyone involved to specify correctly and check for compliance of imported items and products.