Men's Shirt Sizing

Where do you guys buy your shirts from?

The reason I ask is because I've been struggling to find ones that fit. I need a 17" neck, 40" chest, 32" waist. Not a single shirt that I own, or that I have tried on, actually fits correctly. Casual shirts in small and medium won't do up at the neck (or on the rare occasion that they do I find myself barely able to breathe), while even tailored-fit formal shirts are a bit baggy. I was hunting for a plain white shirt in b'ham at the weekend and couldn't find one that fit right between T.M. Lewin, House of Fraiser, Next, M&S and Debenhams. Any suggestions?

EDIT: Should have said, I'm after something I can wear casually, I've got little to no use for formal shirts. I've got no objections to buying a formal shirt, but only if I can dress it down (I.e. I don't want it looking too formal).

So many brands carry shirts, and they all have a different fit. Trial and error i guess.

You could try finding one that approximately fits, and then consult a tailor to see if he can make the final adjustments for you.

I've recently discovered AllSaints shirts for the first time and I have to say, I'm never going back. They fit beautifully, nice and slim just how I like it. Annoyingly it means I'll never be satisfied with a cheap Topman shirt anymore but oh well.