I fly out of London City and stop altitude is 3000'. We normally do stop at 3000' on the BPK departures but soon get climbed and would expect to be at 6000' at BPK where the SID ends.
On DVR and LYD departures we soon get to 6000' and might still be there at DET, but would expect to be about FL200 by DVR or LYD.
When we fly the ALKIN3F arrival, we have to be FL100 at WAFFU, about 100nm track miles from touchdown....(It is very busy airspace)