A couple of points. First, for the LHR arrival scenario, my reading would be to maintain FL150 to the LAM hold, descend to 7000 ft in the LAM hold and leave for the approach at that level at ETA + 10 min (or EAT if given). Don't forget that there are LHR-specific instructions set out in the AIP.
Second, I don't think the European rules are as different as toon makes out. The time from setting 7600 to changing level or speed is 7 minutes, wherever you are. The general procedure if being radar vectored is to route immediately back to the planned track or next significant point. The UK differs only in asking for a 3 minute grace period to sort things out!