I should point out that I have nothing to do with Swiss Radar so I offer the below as comment rather than definitive answers to the original question.
The reason for the frequent frequency changes is almost certainly because of the type of sectorisation used in Switzerland. Because it is at the centre of Europe it has many crossing routes and relatively few airports generating arrivals and departures. In broad terms, most of the ATC problems come from aircraft in level flight at intersections of routes rather than traffic climbing or descending. This means that the most efficient way to sectorise the airspace is horizontally (i.e. a sector covers a wide area but only controls traffic from, say, FL270 to 320). If you happen to be one of the relatively few climbers or descenders it does, unfortunately, mean that you will have to change to each sector as you climb or descend through - but no system can is perfect!
If you compare this to the UK situation, where there are lots of airports generating traffic, many of the sectors cover a geographic area, sometimes quite small, and significantly more levels. This enables the sector to manage the traffic in and out of the airports more effectively - but sectorisation isusually a compromise between many factors, and sadly traffic flows sometimes aren't the determining factor!
As to RTF, as Telstar points out, the UK has quite a good book which has a lot of good guidance which ges beyond (and sometimes differs from) the international standard. I think the limits on what should be passed in a single transmission is generally guidance and probably better described as good practice in an international context. Strictly speaking CAP 413 phraseology etc., where it differs from ICAO Standards, should only be used in the UK - and I'm not sure that there's any real reason to expect anyone in other States to be aware of the UK way of doing things. There's also the problem of what to do when the Swiss version of CAP 413 (if there is one) differs from the UK version.