It is very bad of the CAA to hang on to its VFR charts as they do, letting them out to Memory Map but still only once a year.
Ahem.... The charts are not theirs at all. The aeronautical information is theirs but they certainly don't own the base map. Have a look
here for an idea of the costs involved in using Ordnance Survey maps. The maps may be good, but they certainly ain't cheap.
No doubt if they saw a worthwhile market for the product they would produce it more frequently, however I doubt they wouldn't sell twice as many each year if they published them twice a year.