Rachel Fox has asked me for my definition of "English poetry," one that include Nick Laird (an Irish poet) and Andrew Motion.
It's a difficult question to answer, and I think now that it might be better to talk of the "quietist" poem. Not as in Ron Silliman's rather pejorative "School of Quietude", which is largely a rhetorical device to dismiss a lot of poets who don't fit into his notion of the "post-avant" (I see he now wants to try to encompass flarf & conceptual poetry in the same set as Ojectivism and the New York School.)
But I think it's a good description of what the English Line (to use Neil Corcoran's useful phrase) is about to call it "quietist." Here are a few characteristics I've picked out:
The quietist poem tends to be discrete, both in its aversion to extreme statement, and in the tendency for the poem to be a discrete unit in itself, unlike, say, the often messy, open-ended non-mainstream poem. There's a tendency to irony, to not expressing strong emotion.
The quetist poem tends to be written in a largely rational form, with a beginning, a middle and an end. Its syntax tends to be normative.
The quietist poem tends to be "about something" reasonably discernible - that is, it has one or two subjects and tends to stick with them. The non-mainstream tendency to drift from subject to subject, to slip between meaning and nonsense, is not much in evidence.
Use of chance techniques, improvisation, collage, is not something your average quietist poem will countenance much. Direct use of material taken from popular culture (as in flarf) or technical literature is generally frowned on, though pop cultural references can be used, as long as they're filtered through the quietist frame. Visually, left-justified is favourite, and the visual poem isn't generally seen. It's more like classical music than jazz, for instance. Not that there can't be surprise, as there is in classical music, but the resources for surprise are limited by the form.
These are just a few things I think distinguish the "quietist" poem. There are some very fine poets who fit right in here, so I'm trying not to be dismissive. Not every poem that can be identified as "quietist" will be entirely so. Not everything is as quietist as it appears.
I hope that answers the question, as well as bringing up a whole host of more questions than it answers.