A vote for Bristol.
World's first real aircraft producer - Boxkite series production
First organised flying schools in UK (Brooklands & Larkhill)
First (and only successful) British monoplane fighter in WW1 (M.1)
Bristol Scout - hugely influential early fighter - the inspiration for the Sopwith Pup
Bristol Fighter, hugely successful in WW1, and mainstay of the RAF for many years - policing the Empire : )
Bristol Bulldog
World altitude record breaking Type 138
Britain First, 'executive' aircraft that was faster than RAF's contemporary fighter aircraft, that led to the Blenheim
Beaufort, Beaufighter, hugely successful in all theatres of WWll.
Three influential (if not entirely successful) post-war airliners (Brabazon, Britannia & Freighter)
Pioneering and revolutionary helicopters (Sycamore and 173/Belvedere)
Concord, with a bit of help (and hindrance) from the French
PLUS
all the above powered by Bristol engines - some of the most successful and pioneering aero engines produced in the UK, (Jupiter, Perseus, Mercury, Taurus, Hercules, Centaurus, Proteus, Orpheus, Olympus (Vulcan & Concorde) and Pegasus, off the top of my head), giving Rolls-Royce a run for their money, and keeping them honest
Bloodhound and Thuderbird ground-to-air missiles.
Oh yes, and my dad worked there : )
Not too shabby, though I'll settle for most influential in the UK, up to the Government's merging of the UK industry.