Allow me to correct you
GDPR is EU regulation that did not require EU member states to pass legislation to enact it. However, the UK intends to leave the EU and therefore enacted legislation equivalent to GDPR under the Data Protection Act 2018. See here for more details: http://www.legislation.gov.uk/ukpga/2018/12/contents/enacted
The UK will be a 'third country' once we leave the EU.
Oh I hear you! However as I understand it, under the new DPA laws (which are largely in line with GDPR), the rules are the same regarding sensitive personal data. You can take a look at that here: https://www.gov.uk/data-protection
So, are you saying that it is fine for the estate agents to disclose personal e-mail addresses (which could in every respect therefore disclose someones identity) in a bulk send-to regarding a plot of land for sale?
Maybe I'm missing something here, but I disagree.
