On Fri, 06 Jan 2006 06:41:38 -0800, daddyfreddy wrote:

If you do want to change radiators without altering the width of the
pipework you can buy extendable radiator valves which will accomodate a
slightly smaller radiator replacement.

Or DIY: a 1/2" BSP x 15mm compression Chromed coupler plus a bit of 15mm
Chromed tube will allow you to make an arbitrary-size extension tail piece
which looks quite decent.