I think I might be a bit careful using that method if planning to fly anywhere near the base of controlled airspace. That altitude measurement equates pretty much to a QNH of 1013.
Transponder Mode C altimeter readouts are referenced to 1013 hPa. GPS altimeter readouts are referenced to mean sea level.
I would agree with those who say that UK altimeter settings are far too complicated and therefore prone to human error. Local QNH below TA and 1013 above would reduce such errors (and the likelihood of airspace busts).
I haven't set QFE on an altimeter for 25 years. Given a QFE-referenced MATZ transit I fly QNH plus field elevation rounded up or down to the nearest 100 feet.