I buy UK-originating tickets twice a year or so, rarely more than 1-1.5
months in advance. I seem to get reasonably cheap fares on the dates
I need. I usually buy from consolidators like Trailfinders and such.
Of course, this is just one person's experience, but somehow I doubt
that every Brit on a budget plans his or her vacation a year in advance.

Actually many of us do!

Quite often holiday plans need to be submitted to employers a year in
advance at the beginning of the 'holiday year' - if only to ensure adequate
work cover throughout the year.

My employer works on a January - December holiday year, my partners employer
works on an April - March holiday year. We both have to liaise with
colleagues to ensure that staffing levels are adequate throughout the whole
year.

We are quite fortunate that we don't have to stick to school holidays but it
can be an absolute nightmare for colleagues who are limited by this - they
grab the package holidays and/or flights as soon as possible as you simply
can't leave it to chance to book a holiday for two adults and three kids a
month before you want to go if you are limited to the last two weeks of
July!

My company has a rule that once your holiday dates are submitted then if a
company meeting/conference is scheduled during your pre-booked holiday dates
then you are OK not to attend - I book my holidays as far in advance as
possible!

Having said that, if you can travel at quite short notice there are bargains
to be had - we too have used Trailfinders for some cracking long haul
flights at short notice (we always keep a week or two holiday back for
'just-in-case').

Happy Travels.

Nigel.