Velomobiles and UK Window Tinting Laws?
Yes, window tinting law only applies to motor vehicles.
https://www.gov.uk/tinted-vehicle-window-rules

editing in legal definition of vehicle as per your subsequent question:


  Statutory Instrument 1994 No. 1519: The Traffic Signs Regulations and General Directions 1994 stated that a ‘pedal cycle’ was defined as “a unicycle, bicycle, tricycle, or cycle having four or more wheels, not being in any case mechanically propelled unless it is an electrically assisted pedal cycle of such class as is to be treated as not being a motor vehicle for the purposes of the 1984 Act.”


http://www.bikehub.co.uk/featured-articles/cycling-and-the-law/

A velomobile isn't a bicycle, by virtue of having more than two wheels. It is however a pedal cycle.

Additionally this means that you can have a couple of pints at the pub and ride it back home without having to submit to a breathtest or risk your driving licence AS LONG AS you are not unfit to ride through drink, or pedalling furiously...