I'm booking parking at STN. The BAA website claims 'On-Airport parking just got a whole lot cheaper'. That is of course a BAA lie.
My booking for this week, made in mid-August, for a 2-night/3-day stay in the Mid-Stay costs £28.80.
For a similar booking in two weeks (same times and days of the week), the BAA scammers want £35.20.
For a similar booking in November (same times and days of the week), the thieves want £41.40.

I make that a 44% increase in 3 months, hardly the 'cheaper' in BAA's lie. In fact, the Short Stay Special is only 90p more for that stay.
The point is that there is theoretical competition earning BA Miles using partners BCP and Holidayextras. Their 'discounted' rates turn out to be identical with BAA's, the only difference being that they earn miles, while BAA's earn Worldpoints. (Given that there is a triple points offer with BAA and I am a double points earner, I imagine I will receive 4x points, each worth 1.5 BD or 1 VS mile, so that would have the edge.)
I've no idea what the LHR comparison is as I rarely park there. I'm just disappointed that BA's partners can offer no choice on rates at STN.