Short answer seems to be you need SSL (see below). Slight diversion: if you just need basic data you can get this without SSL via a company URL - example: http://data.companieshouse.gov.uk/doc/company/00001419.json or URI (choose your format).
Someone official said:
This is from Use of TLS/SSL/HTTPS for Searching (Oracle based software)
(which I found using the forum search tool).
Sounds like you just need certificates which can validate the RCA. Under Windows I have experienced some certificate issues around this. Still not quite sure why this is such a pain… Anyway I’d start with the thread mentioned e.g.
After that it’s time for Google.