Thanks for that.
Pretty sure the idle was already raised when I got the DME update - not by a lot but you're right, it made a difference and now it's just a noticeable dip in revs when I come to a stop, but not really low enough for it to shudder.
It used to stall quite a lot prior to this but perhaps it's worth going a little bit higher again.
I have often wondered whether this is just a characteristic of the car/engine, and specifically with the early DBW cars.
The MAF is OK - I swapped it out with another and it made no difference.
I've also pulled the entire intake looking for leaks but didn't find any, even in all those obscure, hard to see places.
And not one code, ever, except when I have deliberately disconnected something.
I've read a bit about these soft failing fuel pumps lately but the trouble is, mine would have to have been soft-failing for about 5 years now and the car otherwise runs perfectly with none of the other fuel pump related symptoms.
I haven't done much with the fuel system though, other than replace the fuel filter so my (perhaps incorrect) assumption that fuel delivery is OK may need a rethink.