For those of us who haven't been on the Perverse Interpretation of EASA Regulation course, you might need to unpack that a little, Pace.
Bookworm
If you read the regulations there are very detailed conditions laid out to comply with legal EIR flight!
Under the usual interpretation of legal flight if a flight starts illegal it remains illegal!
To fly legally IFR under these regulations certain conditions must be met which are VFR / VMC departures and arrivals
Even thought iMC departures are allowed within the UK with an IMCR to do so would contravene the requirements for enroute IFR as laid out in these regulations and hence the rest of the flight would be illegal !
The above regulations need to have added " unless the departure is within UK airspace where the pilot has a current IMCR! In that situation he may depart and join an enroute airway in IMC"
As the regulation is stipulated there is no such allowance made!
As such a pilot departing the UK in IMC would contravene the requirements laid out in the regulation for enroute IFR flight with an EIR once they leave uk airspace, the requirements for EIR flight in the regulations would not have been met
Hence as it reads by departing the UK in IMC under IFR with an IMCR you are contravening the stipulations required for legal EIR flight regardless of what you can or cannot do in UK airspace
To put it in simple terms you fly two flights in the Uk
The first you depart IFR in IMC using your IMCR you fly OCAS to destination and again fly IFR in IMC for the approach and landing
All legal with your IMCR rating
Next flight you do the same but fly higher into CAS for the enroute section!
Illegal in the UK with an IMCR
So for that portion enroute in CAS you revert to your EIR to be legal!
Sadly you have not met the requirements in these regulations with your departure and arrival hence the flight is illegal
Pace