ACROSS
1 - Dizzy blonde? (5-6) - LIGHT-HEADED [DD]
9 - Film, hidden from view on occasion (5,4) - {BLIND} {DATE}
10 - Caricature of girl in opera, lead in Carmen (5) - {MIMI}{C}
11 - Essayist is overwhelmed by extra charge (7) - ADD{IS}ON
12 - Abstemious - tea user, possibly (7) - AUSTERE*
13 - Gloomy day - sail out across mouth of Mersey (6) - {D}{IS{M}AL}
14,17 - Pretty girls using extortion in plant (4-4-8) - {LOVE-LIES} {BLEEDING} Guessed from crossings and this was the last one I got.
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18 - A dry heat out East, all things considered (2,4) - {A}{T T}{H(-e)AT}
21 - Master in pain through most of term (7) - TE{ACHE}R(-m)
23 - Firm not persuaded (7) - UNMOVED [DD]
24 - After hours, a lecturer was wearing (3,2) - {H}{A}{D ON}
25 - He, say, must stand in front of church to make an announcement (9) - PRONOUN{CE}
26 - Argue in protest about WW1 battle charge after commencement of truce (11) – {RE}{MONS}{T}{RATE}
DOWN
1 - Servant, 13, with day off (5,4) - L{ADY*}S MAID*
2 - Old woman, awfully angry, penning note (6) - GRA{N}NY*
3 - Lawrence of Arabia’s birthplace - Democrat misdirected (8) - TERMADOC* Had to google this
4 - Girl’s TV awards (5) - EMMY'S [DD]
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5 - Golden Globe winning actress may make heaviest demand (4,5,5) - DAME EDITH EVANS*
6 - The Lord of the Flies novelist? (7) - D?C?E?S Lord of the flies novelist is Golding, but that does not fit here!
7 - A plank on a ship, perhaps (6) - {A}{BOARD}
8 - Uncommonly splendid manure required? Don’t despair (3,11) - NIL DESPERANDUM*
15 - Ad lib from retired English politician in shot (9) - {EX}{T{E}{MP}ORE}
16 - Warehouse, one pretty nearly bust (8) - ENTREPOT(-y)*
17 - Killer, hideous brute grabbing child (7) - BUT{CH}ER*
19 - Row about Diane being neater (6) - TI{DI}ER
20 - Copper getting a cut climbing dome (6) - {CU}{POL<-}{A} )
22 - Tennis champion served up nine after holding initially (5) – {H}{ENIN} Hard luck to her, she lost to Serena in the Australian open finals yesterday.
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GRID