I buy (nearly) all my shirts from here
Partly because the fabric and construction are (very) good, partly because their standard cut is pretty boxy and so suits my shape.
TM Lewin are pretty arse, but at 4 for £100 you don't feel so bad when they fall apart or you have to bin them as a result of really grim sweat stains etc.
M&S are just arse - they go wonky in shape or colour (or both) after a single wash, never fit properly and never iron properly, presumably because the fabric has been cut in such a miserly manner to get the most out of it.
Years ago I used to buy Pinks all the time. When I went back there a few years ago and tried two notionally identical shirts. It turned out that they had the same overall measurement from the middle of the back to the end of the sleeves, but in one the sleeves were strangely short, and the other the back was supernaturally narrow. Neither fitted and both were a very odd shape. Really not good for > £100 a pop.