Is this the best first comment that you could make?
It seems others agree, so it can't have been that bad ;-) I was also in a hurry.
Although much publicity/media talk does indeed frequently comment that LHR is "full" (or 98/99% so), there still seems to be a fair degree of churn/slot trading on an ongoing basis, as carriers change their schedules/frequencies etc. Not impossible to think that something else will give and this find it's way in, in time.