The reviews are coming in for "The Habit of Art". There are mixed feelings about the play, though most reviewers have written favourable reviews. I give just the bits written specifically about Alex's performance, if you want the whole review, there is a link to the various papers.
Benedict Nightingale writes in The Times: "Does Jennings overplay Britten’s preciosity? Maybe, but he successfully comes across as defensive, insecure and envious of the rival composers he names with a staccato sneer. He’s primly unappetising while Griffiths’s Auden, despite such displays of coarseness as peeing in kitchen bowls, is warmer, more appealing — and, at the end, a bit lost and pathetic."
Full review: Times
Michael Billington in The Guardian: "A play that could easily seem tricksy is also given a superbly fluid production by Nicholas Hytner and is beautifully acted. Richard Griffiths bears no physical resemblance to Auden but he becomes a vivid metaphor for the poet. At the same time, Griffiths reminds us of the tetchy actor who is simply playing a role. Alex Jennings offers an equally potent echo of the angst-ridden Britten, spitting out the name of "Tippett" with calculated asperity.
Adrian Scarborough as Carpenter and Frances de la Tour as the stage manager are no less magnetic."
Full review: Guardian
Quentin Letts in the Mail Online calls Alex "nicely queeny".
Full review: Mail Online
Michael Coveney in Whats on Stage refers to Alex's Britten as "uptight, prissy and over-sensitive"
Full review: What's On Stage
Charles Spencer in the Telegraph: "Alex Jennings is superb, too, as the pained, prissily fastidious Britten and as a college scout grumbling about the squalor of Auden’s room, while Frances de la Tour, as the stage manager, and Adrian Scarborough, as the biographer Humphrey Carpenter, give performances of comic perfection."
Full review: Telegraph