I haven't been to this exhibition, but I can have a go at speculating about some of your questions from prior experience. I don't remember anyone posting on the forum that has seen the Turner and Constable exhibition as yet.
-How crowded do the rooms get? Or lines into Tate?
I wouldn't expect it to be terribly busy midweek in February. One of the advantages of Tate Britain over, say, The National Gallery is the lower visitor numbers. It rarely tends to be very crowded. It's right in the middle of the run of the exhibition and February is a quieter time across all the museums. I wouldn't necessarily aim for 10am on the dot for it opening. If there is any line, it would generally be from people waiting to get in when the doors open. I'd maybe schedule breakfast at The Regency Cafe and aim for 10:30.
-Is the iPhone audio guide suggested on the Tate website useful / helpful?
Tate's audio guides are usually pretty well produced. It's worth downloading ahead of your visit and having a set of headphones to give it a try.
-Is there written information on the walls for each or many paintings (my eyesight is not great for reading those commentaries)?
There will be some information (interpretation) written by each painting. It may just be the title and a date, or something more. Tate went through a period of absolutely minimal interpretation on the wall, which it was criticised for a while back. I'm not sure how they're producing exhibitions right now. Most of the interpretation will be in the app, rather than on the wall.
-Is there a pamphlet to accompany the walk through (before the shop at the end)?
There will be a pamphlet when you claim your tickets before going in, or at the entry to the exhibition. Tate produce nice exhibition catalogues which you may want to buy at the end.
-Would it be good to break up the visit over two days
That would be up to you. The average person is going to see it in one visit.
if anyone has read the recently published book on Turner and Constable by Nicola Moorby I would love to know
I haven't, no. Check out the catalogue when you visit though. A catalogue for an exhibition like this will have some writing about the work and should have well reproduced pictures.
