The number of brands I like and trust is shrinking all the time.
But there are always more ... It will admittedly be slightly more costly (and maybe more troublesome) to order from Europe, but even if one is determined only to shop in the U.K. you're surely never going to run out? Fashion students still graduate every year, City professionals move to villages and start businesses every month ...
I've already listed some places I know and trust, (and whose online sales I'm familiar with) but have you already tried / rejected:
Cawley Studio
Corniche
Envoy of Belfast
Mouki Mou
Old-Town
Some are weird and wonderful, others lean towards the plain and simple - as far as I'm aware all but the last have sales. (And nowadays one sale pretty much merges into the next; times being hard.) All online obviously.
Not that people shouldn't make their own clothes! But I'd be naked if I had to rely on my non-existent seamstress skills. And unhappy if there weren't endless new (to me) designers / brands / shops to discover.
(I honestly never shop at the used-to-be-High-St brands most people have suggested. Toast seems lumpen and hopeless now, and the beautiful linen t shirt I bought from Cos last summer is now mostly holes, despite careful wear.)
(I'm late middle age, btw.)