Don't fall prey to the scammers. They are not selling what they appear to be offering.
There are internet scammers who try to sell what they imply are lists of visitors to exhibitions. Currently doing the rounds are emails saying they can provide lists of visitors to the Natural Stone Show and Hard Surfaces. They do not say these are the exhibitions taking place at ExCeL from 30 April to 2 May, but that is the implication. They are sent from various addresses under different names.
Not only have the shows not taken place yet, so nobody knows who will attend, but the people purporting to sell the information do not have and will never have any information about who visits the exhibitions. Nobody can supply such information because it would contravene the General Data Protection Regulation (GDPR) of the Data Proection Act 2018.
If what they will say they mean by 'attendees' is the exhibitors, you can get that information free from the exhibition websites.
If you pay over any money, there is no guarantee you will receive anything. If you do receive anything, it will not be a list of visitors to this or any other year's Natural Stone Show in London.