I am almost 42, size 10/12 5ft 9" and I wear mainly Gap (for cheap jeans, especially love the long and lean flared ones in indigo, great shape for me) and knitwear - but I only EVER buy in sales, massive discounts to be had! They often have very nice scarves too.
French connection for dressier / nicer day time wear and their jeans / skinny cargos are fabulous. I also have a number of dresses for night time from there too, their stuff suits my shape.
Monsoon for some knitwear (chunky cardigans etc) but only in sales again
M&S autograph & LE for longsleeved t-shirts in nice colours and leggings
H&M for breton tops!
Noa Noa for loads of things, dresses, tunics, knitwear, coats - I really like their stuff.
Boden, I have a few (plain) things from there and like them a lot. But I am selective and don't like loud colours or busy prints.
I used to LOVE Jesire, but sadly they are gone out of business.
I quite like Whistles (but have to admit I liked it a lot more before they changed designer a fwe years back) no local stockist to me anymore either
Jigsaw - similar story to whistles really for me.
Cos - some nice basic bits & jewellery but have to watch the fit as some shapes can be very odd.
Day by Malene Birger - if I won the lotto I would ONLY dress from here 
I always browse in places like oasis and primark but generally stick to places where I know the sizing and fit suit me.
Shoes are a problem area all of their own - I used to LOVE pied a terre but local depart store stopped stocking them and I went into a show decline ! Have been finding some gems in clarks (to my initial horror! Who would have thought it a few years ago!)
I like some phase 8 dresses for night (judicious choices though!) and LK Bennett shoes / shoe boots