You asked
Is it possible to access a database of UK registered companies with SIC code C, for the most up to date year?
We said
Unfortunately ONS cannot make available individual business records. Access to individual records from the Inter-departmental Business Register is restricted by the Statistics and Registration Service Act 2007 and the Statistics of Trade Act 1947. Section 44(1)(a) of the Freedom of Information Act 2000 states that information is exempt if its disclosure is prohibited by, or under, any enactment.
ONS publishes an annual data set of aggregated counts of enterprises by industry and size, which you may find useful.