Zara or even try forever21. I got a casual dress shirt at forever21 for like 10 bucks I think.... decent for the price.

You can also try Espirt, Plenty or even U2 in metro.

gap's got some nice fitting workshirts lately. more towards the american 50's workers look, but they go well with jeans.

tommy's got nice ones too, but not worth the price. their vintage fit is a nice slim fit thats not over excessive

:rofl::rofl::rofl::rofl::rofl::rofl::rofl:

MEXX

I usually check Red Flag Deals of when the 50% sales are coming and buy several shirts for ~$30 each. I like that the shirts are fitted, otherwise to fit in the shoulders usually means it flaps in the wind around my waist.

+1 for zara, their stuff is slim. You do get what you pay for though, materials and construction aren't great though.

You could also try H&M and forever21. Can't really comment on these two though cause i don't own anything from them.

I find that mexx stuff is pretty boxy and over priced.

Giordano in aberdeen... or that just4you store or whatever...
BR is always a favourite

Club Monaco has some very decent shirts that straddle in the line between dressy and casual. Their construction is quite good (can survive several washes without falling apart) and they usually have classic and slim fits.

Look at the fabrics too - some shirts have a slight amount of spandex (2%) that will allow your body to move with the shirt. Avoid shirts with blended polyester; aim for 100% cotton or 95% cotton/5% spandex.