I was just looking for some small sizes of TurboUltra stainless screws at Screwfix and thus searched for 'TurboUltra' and sorted by price. As a result I spotted some bargains on larger sizes, e.g.:-
4.5 x 45 @ £3.54 for 200 5 x 45 @ £4.19 for 200 6 x 110 @ £4.29 for 50 6 x 140 @ £5.59 for 50 6 x 90 @ £6.19 for 100
These are all around 70% reduced.