Hi Mick
I wear a lumbar support and for distance work I find it helps.
In my opinion, (I am an osteopath), the better supports for riding do not have any rigid supports in them but are elastic and will allow good mobility.
The idea of a support is not to restrict movement. The spine is a mobile structure and it is important not to inhibit movement. They should also be worn around the pelvis and not around the lumbar spine for best results.
I use one from a firm called Promedics in Blackburn where I work.
If you want to try one let me know and I can send you more details. I can order one for you and let you have it at cost plus p&p. Approx £30.
David