Via avios.com (so the Avios earned will go into an avios.com account, not a BA one), Holiday Extras is offering bonus points if you pre-book your airport parking through them.
Holiday Extras offer parking at 25 major UK airports, with free transfers to the terminals.
The standard Avios earning rate is 5 points per £1 spent. However, for parking booked and prepaid before 31st May, they are offering 100 bonus Avios for standard parking and 200 bonus Avios for ‘Meet and Greet’ parking.
(Thanks to SDB for this)