Many thanks for the replies so far, and my apologies for not coming back sooner.
Just to clear up a little - this flight will be undertaken in a G registered aeroplane, flying from England to NORTHERN Ireland, where the night qualification is recognised.
Really what my question was getting at may be helped if I give another example, leaving Ireland out of the equation entirely -
Say I wanted to fly (at night) from an airfield in Southern England to, for instance, Oban, assuming in this fantasy world that Oban had the required lighting installed. This crosses an FIR boundary, and would thus require a flight plan. We can now isolate whether it's legal or illegal to make the flight itself, but what would we file within the flight plan? All countries (England and Scotland) along route recognise the night qualification, so that's sorted. But what conditions exactly would you file the flight plan for, in my situation?
Or technically speaking, am I allowed to file an IFR flight plan so long as the only reason for this is persuant to the exercising of my night privileges?
Somebody mentioned in an earlier post that somebody who doesn't hold an IMCR or IR may file for IFR conditions, as this is separating weather from licensing. I only bring this up as I've always been under the impression flying IFR (flight planned, in practice or otherwise), is illegal when one does not hold the additional rating(s), as by telling the enroute ATSOs you are IFR is basically telling them you are competent to follow instructions whilst in IMC, and also that you are trained in IFR letdown procedures and are competent to do so.
I stand by to be corrected, however - my understanding as it lays is based on my flying experiences to date, and this has never been a point that's reared its ugly head before!
Many thanks to all
