Don't know ETHN, but make sure you can land there coming from the UK, i.e. from outside Schengenland. They will need to have some sort of immigration service.
Also, check the NOTAMs for Germany !! They may well have some special immigraion procedures in place for the World Cup (and beware low-flying mugs of beer
)
Always found Austrian ATCOs very helpful and professional (dunno what happened to poor FF there
), so that should be ok. It might be easier however to go IFR the whole way, or at least across Belgium into Germany. Probably gets you a more direct routing, VFR through Belgium is a bit of a pain.