Here are a couple of companies visible in your old API but not the beta. Both were incorporated on 12-Jul-2017. Did you have a glitch that day?
NELCON MERCHANTS (UK) LTD
http://data.companieshouse.gov.uk/doc/company/SC571054.html
M.P.I. LOGISTICS LTD
http://data.companieshouse.gov.uk/doc/company/10862631.html