crewcostcontrol, it's been done here already if you want to do a search but basically "cleared ILS" gives implicit clearance to descend to the altitude that the ils approach starts. If you're vectored towards the LOC at 4000' at EGLL and descend to 2500' (as you might if "cleared ILS") you'll hit a EGLC outbound that's climbing to 3000'.
There are many other examples around the UK but a quick search here will give you a much more comprehensive and accurate answer.