I don't know much about plecos, there are a couple that look a bit like the one your describing that pops up if you google "pleco White seam" ( it came up in the auto complete suggestions!) it looks pretty cool but I'm not sure if it's the right one though, but we will see on Thursday! I think that it sounds most like a 'blue seam bristtlenose pleco' you might have to do some real digging around though to find out anything about it.
Its not that one mate lol but thanks for trying though the size don't really mater as i have a five foot tank lol just want to know what it is will post a pic as soon as loss mateI don't know but I guess they must be there are pages and pages on most fish you see in the shops around here, I also read that it will only grow to around 5 inches, so you don't have to worry about it getting too big for your tank or anything