WDB ACFT DEPARTING AND CLBING FROM LHR; ALTIMETERS SET TO QNH. FLC CLRED TO FL070; USING QNE; BUT THEY FORGOT TO RESET THE ALTIMETERS AND OVERSHOT ASSIGNED ALT. CTLR QUERIED THEIR ALT AND THEY CORRECTED.

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ON DEP; INITIAL ALT LIMIT WAS 6000 FT WITH A QNH OF 991HPA. USE OF HPA WAS NOT A FACTOR. WE WERE CLRED TO LEVEL FL070; DID NOT RESET TO QNE AND CLBED THROUGH FL070. THE CREW OF A CAPT AND 2 ATP/TYPE RATED FO'S WERE FAMILIAR WITH THE AIRPLANE AND OPERATIONAL AREA. THE TRANSITION ALT OF 6000 FT AND THE LOW QNH WERE NOTED DURING THE PRE-START BRIEFING. I WAS HANDLING THE RADIOS WITH ONE FO FLYING AND THE OTHER FO MONITORING. AS THE FO STARTED TO LEVEL AT 6000 FT; ATC CLRED '...FLY HDG 290 DEGS AND CLB TO LEVEL FL070.' THE FO CONTINUED THE CLB; WHICH IS CONSIDERABLY LESS THAN A 1000 FT CLB. TO CONFUSE MATTERS; I MISUNDERSTOOD AND READ BACK; '...HDG 290 DEGS; FL270.' ATC IMMEDIATELY CORRECTED THIS AND I MADE A CORRECT READBACK. BY NOW WE WERE AT 7000 FT (NOT FL070). ATC SOON CALLED; '...CHK YOUR ALTIMETER;' AND WE TOOK IMMEDIATE CORRECTIVE ACTION. SOME CAUSAL FACTORS: 1) OBVIOUSLY; THE CREW FAILED TO RESET THE ALTIMETERS. 2) THE NEW CLRNC ARRIVED DURING THE LEVELOFF MANEUVER AT THE TRANSITION ALT. 3) THE ACTUAL VERT CHANGE WAS RELATIVELY SMALL. A MORE COMMON CLRNC FROM 6000 FT WOULD BE FL130; SO THE RESETTING OF THE ALTIMETER WOULD NOT BE SO URGENT. 4) I MISUNDERSTOOD THE CLRNC WHICH WAS DISTRACTING AND TIME CONSUMING. CORRECTIONS: 1) INCREASED EMPHASIS ON TRANSITION DURING BRIEFING AND INSTITUTING VERBAL CALLS APCHING AND LEAVING TRANSITION ALT. 2) ON A LARGER SCALE; CONVINCE STATES TO ESTABLISH A COMMON TRANSITION ALT ABOVE THE 'BUSY' ALTS.