All our fittings are crosswater, not really through choice, just 'brass, not shit' narrows the search field quite a lot. I did a lot of internet searching to know roughly what I was after, but in the end had a two-hour one-on-one appt with Guy at HE Olby (lewisham) to do some problem solving and see a few things in action. Bought basically everything but the bath through them in the end, a bit pricier than buying here and there on the internet but it sort of paid for itself when some things needed swapping/replacing.
I'll second HE Olby - very easy to deal with when there were a string of fuckups with our porcelain (first two bog pans arrived damaged, first sink had cosmetic problems, replacement was the wrong variant of the model we wanted), including giving us replacement taps because that was a better result than swapping the basin again.
In terms of brassware, Hudson Reed stuff is reassuringly solid, and not a silly price when you factor in the 10 year guarantee, which they're happy to stand behind. Obviously we'd have preferred the thermostatic mixer body not to crack, but they replaced the (£300ish) part on the basis of one phone call and emailed proof of purchase.