Demister only required if there is provisions for a roof.
So having ferrules and a full size screen they would have made you fit a demister, because the option is there to fit a roof.
My car when complied had aero screen and no ferrules, so I did not require wipers, washers or demister.
This is mine the day of compliance check.
No quick jacks, aero screen, headrests, heat shields on side pipes, no spinners on rims etc.
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Cruising in 5th
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Never be afraid to do something new, Remember, Amateurs built the Ark: Professionals built the Titanic.