Bougainvillea spectabilis is probably the toughest and conveniently is
the most commonly available. That said, it will not survive out of
doors anywhere north of the southern-most counties and even then only
in the warmest, most favourable spots where air-frosts are infrequent
and very light. So Formby or anywhere near it is far less than
ideal. For a Bougainvillea to survive, the colder the night, the
warmer the corresponding day temperature has to be. If fairly dry at
the roots, Bougainvillea can survive a couple of degrees below zero
for just a few hours provided there's a compensatory rise between 8
-15C during the day.

However, it will suffer badly if there are frequent exposures to sub-
zero temps or if several take place within a short time. Even in
relatively frost-free regions, there are problems since cool
temperatures combined with moisture at the root and high humidity can
lead to root rot and boytritus, which will attack and kill buds on the
stems. B. spectabilis needs to be planted close to a warm, sunny wall
where there is 'rain shadow' to prevent the roots becoming saturated
in winter.

The hybrids with pink, orange, red or white bracts tend to be less
cool tolerant and are best kept 'ticking over' with a little root
moisture, full light and temps above 3C. by night rising to 10C or
more by day.