+ 1 for Banggood corner clamps. * * * * * (5 stars).
Found these extremely useful when helping a mate build a king-size bed recently. Indispensable if dry-fitting on your own.
Checked for "true" with my Incra Guaranteed Square: Spot on!
Also, for info, the OP quotes the price of just the right-angle brackets (6-3/4"/171mm). Woodpeckers charge another £37.50 (pair equivalent) for the threaded angle-bracket thingys.
Banggood are currently selling a pair of the 160mm version (with brackets) for less than the price of the Woodpecker angle brackets (£33.20 + free shipping). Notwithstanding the lengthy delivery times, the sporadic up and down discount pricing, and acceptance that returning an item (under some sort of equivalent 30 day return policy) is cost prohibitive, due to the cost of shipping anything to China; but if you are on a budget, it's worth taking a punt IMO, especially with the Veiko, Hongdui, DrillPro brands.
**
Incidentally, I have purchased A LOT of woodworking accessories from BG (damn that Dennis from HookedOnWood!), half of which is a copy of either Woodpeckers, Bessey, Incra or Festool. Resultantly, I am extremely happy with 24 out 25 of my purchases, but they have been carefully selected.
Admittedly, the thought of buying Chinese mass-produced items does not exactly fill me with joy, but at least buying through a YouTubers affiliate link is one way of supporting the people who have taken a lot of time to present the content that many of us find so invaluable.