Yes, part of the Brexit agreement was the UK "domesticating" some parts of EU law by passing them as UK legislation. There is now a law called UK-GDPR, which is literally a copy-paste of GDPR, with names of EU institutions find-and-replaced with their UK equivalents.
There are still some operational differences, around the fact that the UK regulators will not participate the cooperation mechanisms that the other regulators will. This ends up mattering for businesses: a significant aspect of GDPR was that a company only ever had to deal with one regulator, but now they need to interface with one for the EU and a second for the UK.
I believe GDPR is supposed to be implemented in every participating country's legislation, so the GDPR was implemented in UK law and this remains the case even after Brexit. Nothing prevents them from amending that law and repealing the GDPR's effects on it though.
There are still some operational differences, around the fact that the UK regulators will not participate the cooperation mechanisms that the other regulators will. This ends up mattering for businesses: a significant aspect of GDPR was that a company only ever had to deal with one regulator, but now they need to interface with one for the EU and a second for the UK.