Perfect summary. I'll add one more consideration: risk profile. UK domestic shipping essentially eliminates customs risk. Your package is a domestic parcel moving through Royal Mail's standard network. No Border Force inspection, no HMRC flags, no "your package has been detained" letters. China direct always carries a small seizure risk (I've heard estimates of 2-5% for peptide shipments). QSC offers reshipping for seized packages, but that's another 3-week wait. With UK warehouse, the risk is transferred entirely to QSC's bulk import process, which they seem to have figured out. For peace of mind alone, the small price premium is justified.