Slip n Turn
I must step in and back up roffa here
London City departures do NOT affect Heathrow inbounds. City departures climb to 3000 then further climb on the SID when instructed by radar, Heathrow arrivals decend to 4000 = separated in my book.
In regards to where the Heathrow aircraft do their turns onto base and finals, this is purely down to conditions of the day (winds etc), amount of traffic and runways in use at Heathrow, and also who's controlling at the time I guess!! (I dont do radar!)
Hope that helps Slip n Turn
Roffa hope this backs you up!