First of all, there is no such thing like "The filters developer says it seems like a template/layout problem". This is can't true, and it is not logical.
The reason why this is happening is mostly because:
"That filter plugin has been developed to work with official Virtuemart browse page", "or the filter extension is developed to work with some simple 3rd party Virtuemart templates". But you are neither using official Virtuemart category page layout nor simple 3rd party simple Virtuemart template. You are using very complex VM template: CleanMart, which includes a lot of unique features that no any other VM template has. "multiple thumbnails in category page, showing manufacturer icon in the category page, 3 Views on category page, showing percentage label etc..).
Therefore, it is obvious there is a conflict issue. Sometimes a 3rd party extension doesn't support an another 3rd party extension (be aware: both our template and their filter plugins are 3rd party extensions for Virtuemart). Blaming another extension/template is the "simplest" thing to do, which is i believe what the filter plugin developers did. I am sure they didn't even check anything on your website, as soon as they noticed the "3rd party template", they blamed our template for the problem.
Actually i noticed something in your website,
please open these 2 URLS:
www.dusk-led.co.uk/interior-led-lighting/led-ceiling-lights.html
www.dusk-led.co.uk/lighting/led-ceiling-lights/
those 2 pages look the same. The 1st one shows the percentages correctly, but the 2nd one doesn't. Did you notice that? And, if they are the same exact page, then why there are 2 different URL's to reach the same page?
Disable the SEF URL and check if those 2 pages' non-sef URL are also the same.
Regards,
Support