we are taking GDPR compliance very seriously and we are warning all users who decide to use their email to create an account that they will receive all related emails to the order including the Review email request and that they can always unsubscribe or withdraw consent from receiving emails as outlined in the Privacy notice for riders
Regarding SEO value of your reviews: we are doing our best to deliver as much value as possible and you can see some SEO benefits by checking https://drivenot.com on websites like this one
People may not be coming to your website from DriveNot yet but this might be simply because no one is looking for your company online. You can notice in a Google search result for your company that drivenot.com is ranked in the first place and it also shows your excellent review results
Hope this clarifies things.