It appears the EU directed the UK to change when
the summer ends (thanks Foryth)

http://europa.eu.int/eur-lex/pri/en/oj/dat/2000/ce337/ce33720001128en01360137.pdf

I have munged the Unix zic(1) tables to plan9 format by hand,
however I have done only /adm/timezone/BG-Eire. 

The tables all expire in 2038 of course...

PS. Forsyth hinted dhog might have had some code to do
all this in a dusty corner of the labs venti.

-Steve