*bump*
-----UPDATE-----
I had a meeting with the MD yesterday, about my request for a review based on the amount of work I'm doing.
First of all, he told me off for writing an email to him and HR, and said I was 'dragging other people into it'. The email was copied to my temporary line manager and the MD's deputy (who said if there was anything he could do, then let him know). The MD said he'd told me not to do anything rash - I didn't, I wrote a considered request several days after the event (and I didn't tell them to stick their job up their arse) - and that the email didn't 'endear him to my situation'. He also told me he didn't bother reading my email as 'it was obviously asking for more money'. I pointed out, tactfully, that it made no mention of money, other than to refer to the salaries that the other positions are being advertised at.
He then told me I'm abrasive (no example), I need to adjust my attitude a bit (no example), my social skills are lacking (no example), I'm too accomodating and I need to say no more often, and perhaps I should 'run things through my head before saying them out loud.'
He acknowledges I'm overworked at the moment, and he's worried my health will suffer (I did not point out that attacking someone's personality when you barely know them really helps their stress levels

), and he's trying to get someone to help me (yes, well, one of the jobs I'm covering has been open for 7 months, and they refuse to give it to the internal candidate at another office, who would be great at it, really helpful

).
BUT:
he also said he would give me a one-off payment in recognition of the extra work I've been doing, and he said I was a valued member of team who's contributing a huge amount.
Call me cynically, but it's hard to believe the positive stuff after such a negative start, and until it's written down in black and white, I not counting on anything.