Jane .... I'm coming into this late in the piece, but if you think how you'd respond to a TCAS RA then I reckon you ought to give the same urgency to to an instruction from a controller such as you described - the situation probably isn't that different.
I've had drivers airframe quibble about headings issued to avoid traffic on the basis they'd fly into cloud - I usually offer them some non standard phraseology giving them the choice of flying thru either water vapour or aluminium and they then see it my way.
I also think that although standard phrases are fine 99% of the time a controller can encourage pilots to give it their all with the use of the occasional colloquialism!
