"Mike Dodd" wrote in message
...

We've a set of patio doors, with three hinges per door, in white. Each
hinge comprises the mechanical hinge part, and a steel clip-on cap,
painted white.

Here's an example of a "good" one:-

http://summat.co.uk/DSC_0027.jpg


Have you tried contacting the original fitters for help? They might be able
to tell you who they buy their fitting from.

Or have a web search for "hinges with covers" or the like.