Watching with interest as I'm literally the same - height, weight, body shape - spooky!
Definitely no need to go to plus size shops imo, most of the high st and online covers up to at least size 18 - I'm a 12 or 14 in most places for tops and a 16 for trousers. Are you about the same?
There's no denying that better quality stuff is often more flattering - better cut, nicer fabrics etc. I find having a few decent items in your wardrobe (including non-figure related stuff like bags, shoes, jewellery, scarves) really helps, then you can get away with mixing in cheaper stuff. I don't spend a fortune but rarely buy from higher end places without a discount code or I wait for the sale.
Off the top of my head I like:
(Pricier end) Hush, Mint Velvet, some of the John Lewis own brands like Kin and Weekend, plainer stuff from Joules/White Stuff/Boden, The White Company, Gap although it's not as good as it used to be
(Cheaper end) Primark (choosing carefully - I've had stuff that's lasted 1 wear and things that are still going years later), H&M, New Look, Sainsbury's, Next Clearance section especially for Petite jeans (I like the Lift Slim and Shape ones which you can get for around £20), TK Maxx
I find dressing in Autumn/Winter a million times easier - not only because you're more covered up but because I find the styles, fabrics, colours etc more flattering.