The EC sales list export cannot be uploaded as is to the HMRC website. Errors meant I had to edit this before uploading it to the HMRC site.
a) The Country code gets repeated in the VAT number (so HMRC reports incorrect VAT number)
b) The amount column includes pence, so HMRC reports "csv contains decimal point" - should only be a whole number
c) One of my sales was done using reverse charging. There does not seem any means of indicating this on Kashflow, so the indicator column was incorrectly set to 0.
(raised as a support ticket also)