Thank you all for your tips and in particular Chris's RHS link

http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=60

I will split it in half in Spring and move it to the back garden, where it
will be protected on 4 sides and will get full sun from mid morning.

Living 500' up in SE Cornwall doesn't guarantee plant longevity. During the
Winter of 2010/11, I lost a 6 year old wisteria from the back garden. Took 3
Summers before flowering - grrr.

Thanks again and fingers crossed. I may not get flowers till 2015. I'll dust
the wounds with sulphur powder in Spring.