Remove email check against registered users for guest checkout

-- HikaShop version -- : 3.2.2
-- Joomla version -- : 3.8.4
-- PHP version -- : 5.6.33
-- Browser(s) name and version -- : chrome
-- Error-message(debug-mod must be tuned on) -- : Email is already used

the site sells tickets for an annual event and the odd event in between - because its annual users don't tend to login and use their accounts instead they prefer to enter the info needed and be done!
Am starting to sell t-shirts now too but the password reset is too complicated fo the users (yes they are thick!)
My intention is to remove the login facility and just have guest checkout but if a user has already registered the error message "Email already in Use" pops up - is there a way of disabling that email check?
I have set the Allow registration after guest checkout to No but am still notified about the email!

Any ideas would help -thanks