Yes, Mark Perryman was/is a member of Respect and stayed in the half that supported George Galloway, and not the SWP.
Here's an article he wrote about left politics in general, and Respect in particular
http://www.redpepper.org.uk/Agency-for-change
A couple of very sensible points he made in the article were (1) He acknowledged the strength of the SWP, and, despite disliking them, wrote that the Stop the War Coalition wouldn't have existed without them. (2) He criticised narrow approaches to building alliances as "a politics whose sum total of alliance building seems to stretch as far as the Morning Star and Bob Crow"!
Albert