An expert friend in discussion this morning affirmed that in this case the right decision has most certainly been achieved.
Retuning an instrument of Mander's quality is no small task nor can be undertaken lightly with any real liklihood of reversibility in such circumstances. The modern revival of traditional methods has caused the easy tuning system of sliders on pipes to be considered second-rate - which they are for, as easily as they can be tapped for tuning, they can slip on the pipe resulting in the pipe going out of tune just as easily. Instead, the best of organs, and in particular in the perfection of modern instruments, pipes are cut to size to their calculated length for the temperament concerned and cut to length on voicing . . . and fine tuned in situ with cones forcing the end of the pipe inwards or splaying it outwards. This is a pretty permanent tuning technique and offers maximum stability.
Furthermore at the recent talk to teh Surrey Organists' Association, Matthew Copley explained how the tone of reeds is affected by the length of resonator coupled to the tuned pitch of the pipe. The resonator is literally cut to length with a knife on voicing. This means that retuning means a change in tone or alteration of the length of the resonator. As in Kellner C is 8 cents sharp if one tunes on A rather than C, the resonators will be too short for equal temperament. A change in temperament therefore is not a temporary alteration.
The decision of the delay by the year before undertaking the change is so very musicologically important and hopefully the school might be sympathetic to visiting organists and local Orginists Associations . . . as well as trying out in particular early and mid 19th century repertoire for concerts and recordings.
The progress through the opinions discussed on this thread is also testimony to the value of full, open and frank discussion of all opinions and levels of assumption and expertise. It's through good discussion that people find harmony, ideas are more widely understood and the best decisions are reached.