Andrew bennett wrote:

Hi I just wondered if anyone else has had any luck growing this shrub
outdoors in the uk? I have a plant that i brought back from the south
coast of Sri Lanka,

That's travelled quite a lot then - S. America to Sri Lanka and then
London ;-)

Pure B. pauciflora and possibly its cvs Floribunda and Eximia can cope
with short periods of cold and ultimate lows of around -4C if
moderately dry at the root. Unfortunately, it appears that most of
Brunsfelsia sold in this country nowadays are the large-flowered,
deeper coloured 'Macrantha' cv, which is decidedly less forgiving and
not really safe below 0C for any length of time.

I've overwintered 'Macrantha' outside here a few times, but to suggest
it coped well with the experience would be a major exaggeration on my
part. Generally, away from favoured regions of the south-west and
urban heat sinks such as London, all Brunsfelsia need to be wintered
frost-free under glass.

Back to yours, which is probably the more cold tolerant 'straight'
species, if I had the plant it would be sited in dappled shade and I
wouldn't think twice about planting it out permanently. If last
winter in your part of the country was typical, then it's a fair bet
yours will survive outside again. Planting with some evergreen
overhead cover will greatly enhance its prospects since rapid freezing
due to exposure to clear open skies often does far greater damage than
sub-zero air temperatures. HTH