There are a couple that post on here: Michael Peoples from McCambridge Duffy and Lisa Thomas from Neville and Co, a few biggies like Stepchange and Payplan, along with the likes of Aperture and Creditfix. All are reputable, though some are not too sympathetic and like things their own way --- there are hundreds of others ... have a "Google",
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014 http://foggy.blogs.iva.co.uk