UKHO official data - and all other hydrographic offices data - is held in a vector format. Currently held in S57 standard format but in the process of moving to the S100 series of standards which allows more enriched data (mostly not about the charts themselves but other aspects).
Paper charts are derived from these vector master sources, but generally currently requires manual intervention to determine how best to represent some details - and hence very expensive to produce (perhaps AI will be used to maintain the option of paper charts for a bit longer). Hence paper charts are often less up to date than ENCs.
The UKHO doesn’t as far as I know actually print any paper charts - these are done via Print on Demand by Admiralty Chart Agents.
Electronic Navigation Charts (ENC) are the official vector charts required to be used on large commercial ships on their highly regulated ECDIS systems. These are very expensive compared to leisure charts - make that EXTREMELY costly compared to current leisure charts if need a wide of coverage, like a current Navionics card.
The MCA (not RYA) have in MGN 319 decreed that small coded vessels (including charter yachts and training yachts) can ONLY use paper charts or their SVECS system with the expensive ENCs. Personally I think that is a mistake, and I don’t know if the MCA understood the scale of cost differential when imposing that rule.
Also, whilst official ENCs are great for waters used by large ships, they often lack essential data needed by leisure craft in inshore waters - eg layouts of yacht marinas etc. Plus they can be very slow to update in places like river entrances with shifting sand or shingle bars.
Official UKHO charts are good - but NOT always the most up to date or accurate compared to some commercial leisure charts. Many of us on here have hit rocks not shown on official UKHO charts.
