If I may answer the OP with some hard facts of the outdated and misremembered sort…
Years ago I wrote a piece (that very certainly sucked), and wondered what it would cost to hire the local professional orchestra to play it (in a studio setting). I would have been the conductor (although this was well before I learned to conduct. Or compose. Or orchestrate.) I spoke to a Mr. Dumm, a horn player and contracter with the Rochester Philharmonic Orchestra. There was a flat fee per musician per hour. Time and a half for doubled instruments, I believe. I did the math for a smallish orchestra for maybe 2 hours work and it came out to something like USD3000. That was 25 years ago.
The less-good scratch orchestras are ones with no permanent members, the whole ensemble being bought in freelance for each concert. Sometimes this means they get a top-class lineup, and on other occassions it’ll be full of players incapable of getting a permanent professional position, students, etc. So they’re nominally a professional orchestra, because everybody’s getting paid, but sometimes the players are the same standard (i.e. the same people!) as in good amateur or semi-professional groups.
What I mean in reference to Bournemouth and the RLPO is that they aren’t necessarily going to produce a worse concert than the LSO, but due to their less prestigious reputation, they cannot command the same money (or the same audiences). Think of it as comparing the New York Phil with perhaps the Dallas Symphony.
Most film sountracks in the U.S. that use a real orchestra hire out session players, not an existing ensemble. There is little or no rehearsal time; you read it through it once, and then you record it, usually several takes. Snarky comments about the LSO being a supposedly better sight-reading orchestra than U.S. professional orchestras are just stupid. Having done some of this myself, I can assure you that the vast majority of soundtrack scores are eminently sight-readable by any self-respecting professional musician.
In point of fact, U.S. orchestras are notorious for their parsimony toward the number and length of rehearsals, compared to European orchestras. Over the years, a number of first-rank conductors who guest conduct American orchestras have complained about not getting as much rehearsal time as they wanted.
We’re getting sidetracked by focussing on film scores. I fully agree that most are simplistic and straightforward - but the Star Wars ones certainly aren’t typical in this respect.
It’s not intended as snarky, and it isn’t specifically about the LSO, but about the general orchestral cultures. It’s an observation I’ve heard many times, from people on both sides of the pond.
I’ve gone in search of first-hand comments, and found Corigliano bemoaning that orchestras often get ‘as few as three or four’ rehearsals, for full concerts including new works (I’m paraphrasing). My point is that while this seems to be a cause for complaint in America as an unacceptable and drastic situation, it’s standard and accepted practice throughout every level of British orchestras, professional & amateur.