Thanks all, it's very helpful to hear what you would do.
Dellzeqq, that's a beautiful bike
They must be very small tubes though, I struggle to fit everything in my top-peak saddlebag with just the two.
The idea earlier of strapping a tube underneath the saddle was a brilliant one, but despite struggling for some time, I just don't quite have the room under there.
I've decided to stick with two tubes, I've put the other in one of the water bottles as I only ever use one through the Winter anyway.
I was going to stick to one, but changed my mind cycling in this morning.
I have to travel through several quite wooded sections on the way in and already it's quite gloomy through there.
Despite being a hairy-arsed bloke, the thought of sitting amongst the trees in the dark with the wind howling through skeletal branches whilst the local fauna crashes and shreaks around me does not instill feelings of deep joy and contentment.
Actually, I wonder if I could fix a Brompton to a rucksack......................