Having read this thread I have entered the primary email into the 'main receiver' field, which was formerly blank, since the primary email is the same as the site-set-up email. No VAT payments are configured in CBSubs or in Paypal;
Since making this change and editing this post; I have received a successful payment with the approproates entries in payments and notifications, so this begnis to look like ths olution;' if so, then the notes about configuring the payment gateway in CBSubs mislead me to think that this 'Main Receiver email' field needed to be filled only if you hade several businesse on the same paypal account; we have only one, but it does have two emails

Typically it's best to configure PayPal Business (email or secure merchant ID): to your merchant id and PayPal Main receiver account (email) (if Business is different from your main account): to your primary email address attached to your PayPal account. The Business scenario only applies if your PayPal account is an actual business account (you need to apply and likely pay for such through PayPal, a premier account or account in general is NOT a business account).