Thanks for your comments!.
You can still get the old 1 1/4" tubes here but they are pretty rare, which is a good thing, considering the mercury content that they have.
T8 (25mm) is the most common type of tube here these days and with the advent of Tri-Phosphor tubes, with next to no mercury in them and a lot better light output quality, I would imagine they will be around for a wee while yet.
However, they would (I would imagine) be used in conjunction with HF ballasts.
I'm not going to be shedding any tears when the last Wire-wound ballast finally gets put to rest.
Fluorescent fittings are a lot lighter and easier to fit, with HF ballasts in them and without the heat dissipation.
The only aspect of the new T5 fittings that I'm not sure that a lot of people realise is, the fact that maximum light output is attained when the tubes are at an ambient temperature of 25-30 degrees C.
I'm not really sure how achieveable this would be in a normal installation.