I recently opened the boot of my husbands XKR 2007 convertible before he had completed the roof closure. This has caused an expensive repair to the window regulator. I have spoken to several people about this and they are of the opinion that the boot should not be able to be opened during this procedure. Does anyone have any information on this.

Opening the boot stops the operation of the roof. It does not cause the window regulator to fail. If your window regulator failed at that time, it is likely coincidence.

Give us more details. After you closed the boot again did the roof refuse to move? This will often happen if the roof is stopped midway for more than a minute or two and requires a roof reset procedure.