I really need to get this working. It's been bugging me for ages and preventing me from moving forward. And I would be happy to pay for a solution.

By what mechanism would this NOT work, (remove the spaces)
http://one stop glasses .co .uk/index.php?main_page=index&cPath=55&fltLens_Width[]=51

When this does,
http://one stop glasses .co. uk/index.php?main_page=index&cPath=55&fltColour[]=Black

I've spoken to to my web hosts/designers but they don't work with Zencart, there is a danger of the site being rebuilt with Opencart which would be a tragedy as the above is my only real problem.