Further Info: I had a reply from my email to the JAA Medical section...
The colour lanterns which are acceptable to test colour vision for a Class
1 medical certificate are only those you mentioned as set out in JAR-FCL
3.225 (b).
(...and they are the Holmes-Wright, Beynes and Spectrolux)
For acceptance of licences see JAR-FCL 1.015 (a)(1):
Where a person, an organisation or a service has been licensed, issued with
a rating, authorisation, approval or certificate by the Authority of a JAA
Member State in accordance with the requirements of JAR-FCL and associated
procedures, such licences, ratings, authorisations, approvals or
certificates shall be accepted without formality by other JAA Member
States.
Please note that the initial medical certificate has to be issued in the
State of licence issue (JAR-FCL 1.065 (a). The aeromedical examination for
revalidation of a medical certificate can be performed in any JAA Member
State.
All of the above is only valid for those JAA Member States where JAR-FCL
has been implemented and a satisfactory standardisation visit has been
carried out. So far these States are: Denmark, Iceland, UK, France,
Switzerland, France, The Netherlands, Sweden, Finland, Malta, Spain,
Belgium. Please take into account that after implementation of JAR-FCL the
State of licence issue remains responsible for the licence which is only
valid with a valid rating and medical certificate and that some national
differences may apply. Please inquire with the National Aviation Authority
in the country where you intend to fly whether the medical certificate is
valid without further administrative requirements.
...and also in a recent letter from the CAA, they merely state that they use the Holmes-Wright (despite my asking if there were any plans to change to perhaps Nagels Anomaloscope), so I can only presume they have no plans to change. However, the letter also states As colour perception is unlikely to change, there is no requirement for five yearly retesting.
I don't know if any of this is useful to anyone here, but I thought I'd post it anyway.
I wonder if anyone from the CAA reads these threads - any thoughts ?