I had a look at some in M&S a little while back but opted for ones with out an underwire instead as the ones I had were too uncomfortable.
I've got one with good lift but it puts a lot of pressure on my shoulders which is painful and another one which is more comfortable there but doesn't have the lift (was an underwired bra but I took the underwire out).
Maybe time to look at the sports bras then! I've got one somewhere, got it after an "experience" trying boxercise years ago in a normal bra, nearly knocked myself out.
Have you considered a post surgery bra? I know you haven't had surgery but they are supposedly far more comfortable than traditional underwired but have decent support unlike sports or Belvia bras.
I too am big in the boobs and looked in at this question because I had been meaning to ask it ! I liked the look of the Belvia ones , now I am pleased I did not buy one. One day a manufactor will make one for big girls.
I haven't Daffy but will go have a look at some, hadn't thought of that!
After I had my gallbladder out I couldn't wear a bra for about a week and it was lovely not feeling all trussed up! I wasn't out much save getting one of the wound sites treated as it was infected and covered up with baggy stuff and a coat to hide it but wouldn't be able to do normally and not good for your back I guess.
Have you tried Bravissimo? They have high street stores so you could try the bras. They go up to L cup and should be able to give you professional/expert advice. http://www.bravissimo.com/products/lingerie/#/1
The best comfort bra I have found is from Evans it is their non underwired 'firm' range - 2 for £24 they are so comfortable I now wear them all the time.
I have tried them as well all right if you are small busted not suitable for big breasted women, ok for lounging around in but not much support. The adverts for them make out that anyone can wear them but not true, no support in that!