VW T4 Panel van rear Seats

[phoenix320]

Hi I have a LWB T4 panel van, and I bought two single seats in matching inca fabric with integrated 3 point belts from eBay. I want to fit them but have been told that you are not permitted to fit rear seats unless the rear has windows (i.e. it is illegal ?), Is this true ?

Once fitted do I only need to get a new M.O.T to insure it or is there any other certification required ?

In addition can anyone recommend an insurer that will insure a modified van since my current insurer will not.

Thanks in advance.