Hi and well done!!
Well for Heathrow there is genrally a 3 month waiting list. I got offered the job, then heard nothing for one month, then they rang me with a start date for 2 months time. My interview was in March and I start June 20th.
Don't worry if you dont hear anything for a few weeks. this is perfectly normal and many others have experienced exactly the same!
Well done again! C u in Heathrow this autumn