At Heathrow, if you give the correct QNH on first contact (along with type, stand, ATIS letter etc), then you have it as far as we're concerned. In fact, Stansted use the same electronic system as us, and we note on your flight strip that you've given the correct QNH. I can only assume Stansted is the same. So I'm not sure why they transmit the QNH again, forcing you to read it back.
Anyone from SS here?