but Flymap superimposes flight plans, provides weather data, closest airfields, i.e. all the usual goodies but using the CAA charts
Have you actually seen this work?
The problem is that the CAA doesn't appear to let out their database in a "database" form; they let it out only as a raster image. This is what MM gets, which is why they product is just a dumb raster display. MM has no concept of airports, etc. except possibly via the georeferenced airport diagrams which are included with MM.
It's only the Jepp vector database that allows you to "right click" on an airport and see its properties, etc. If Flymap does that too, I'd very much like to know how they did that. The data has to come from somewhere. The UK AIP is not released in a machine readable form and neither is anybody else's (except probably the USA) and this is what keeps Jepp in business.