UPDATE REMARK 9/11/2006:Interesting note here identifying that ITV can't always spell its stars' names correctly. They're not the only ones to do so as I have come across other references to Douglas that spell his name that way. And not just the often unreliable range of DVD sellers and film sites.
The ITV error mentioned below has now been corrected!
Amazon.co.uk do it here for the recent release of Down Among the Big Boys. For the US book "The Scot Pack: The Further Adventures of the Trainspotters and Their Fellow Travellers" (2000), Amazon.com has two reviews: one by Publishers Weekly gets the name right as Douglas Henshall (there is apparently a chapter on him in it), but the second promo lit review by the Library Journal mentions him as Douglas Henshaw (did they not even read the contents page of the book?!).
Over at Textualities, they have an interview with Christopher Brookmyre where they transcribe his remarks about his preferred actor for the role of Jack Parlabane in "One Fine Day in the Middle of the Night". There's an MP3 link at the bottom of the page saying you can "Download the original audio recording of this Q&A session to hear the author's opinions expressed in his own voice." I wish they had bothered to check the spelling of Douglas Henshall then, rather than going for Douglas Henshaw.
But even photographers seem to get the name wrong, as here for example where you can scroll across to view the delightful image that hangs in my left sightline behind this computer in my study. Maclellen's picture is divine, but the spelling to me suggests one of two things: either the name is deliberately spelled to avert excessive interest (seems unlikely for a photographer who might want to sell their most desirable prints); or the photographer believed that was the accurate spelling.
Either way, it wouldn't take much to work out that the majority of spellings are as "Henshall". For both Dougie and Douglas Henshaw, the combined google results are just 510. For the same with Henshall, its 91,640. Now go figure why Amazon (or even ITV) cannot get the name right.