Adrian Brentnall wrote:
If I leave some side-shoots to develop, will they bear flowers & fruit -
or is there something 'special' about side-shoots that they don't bear
fruit ?

I quite often let the side shoots grow, and they flower and fruit like
a main stem (pretty much). Nick's mum hates how I treat my tomatoes
(she religiously nips out the side shoots), but if one goes wild and I
don't catch it whilst it's still small, it seems mean to cut it out
when it has put so much energy into it!
(I've also had stems that have been accidentally snapped, and let a
side shoot take over as the new main stem, which has worked fine)

Of course, you'd have b een better off if you'd got bush tomatoes in
the first place. :-D