Email says 10% or 20% of for clicking the link.
Edit: Credit to @Darthhasbro for the 20% off code SPOOKY
If anyone wants to put extra cash into the BNE airport coffers BOO will give you 10% off instead.
Special available for bookings made before 12pm, 5 November 2017 or until sold out earlier. You are entitled only to the discount associated with the code in your email. The voucher code set out in this email may entitle you to a 10% or 20% discount off selected parking products.
SPOOKY for 20% off