Across:
8 Charge (GALLOP) everyone (-ALL-) in The Republican Party (Grand Old Party = G-OP) (GALLOP),
9 Writer (-PEN-) in Essex (Essex = EX-SES) (EXPENSES) negotiated overheads (EXPENSES),
10 Form of (TYPE) work in the office (TYPE),
11 Rustic individual (COUNTRYMAN) offering to go, for instance (Togo = COUNTRY-), with worker (-MAN) (COUNTRYMAN),
12 Ripens (ripens = SNIPER) bananas (= anagram indicator) and gives it his best shot presumably (SNIPER),
14 One offering unstinting support (LOYALIST) is silly to a (silly to a = LOYALIST) fault (= anagram indicator),
15 Ha! That’s funny (AMUSEMENT) hearing (= homophone indicator) Mal (“Mal” = “mall” = ARACDE) (AMUSEMENT ARACDE) is entertaining on The Prom? (AMUSEMENT ARACDE on the promenade),
18 Young footballer (MINOR-) is not starting for Dublin, for example (not starting for Dublin, for example/ ‘city’ = - ITY)) (MINORITY), and that’s not even the half of it (MINORITY),
20 Sounds angry (yells), almost (s) (‘yells’ without ‘s’ = YELL-) short (low), losing the head (l) (‘low’ without ‘l’ = -OW) (YELLOW) with cowardly type (YELLOW),
22 Escape (FLIGHT) route (PATH) (FLIGHT PATH) – of course, it’s only for the high flyers (FLIGHT PATH),
24 Sample of cheese – a luxury (sample of ‘cheese – a luxury’ = SEAL) in Cork (cork/lid = SEAL),
25 Ring (ENCIRCLE) for the last of the beer (last of the ‘beer’ = -R-) in off (= anagram indicator) licence (license = ENCI-CLE) (ENCIRCLE),
26 New (N-) range (oven) isn’t finished (‘oven’ = -OVE-) for heartless (remove middle = ‘as’) lass (‘lass’ without ‘as’ = -LS) (NOVELS) telling stories (NOVELS).
Down:
1 Could start (‘could’ start = C-) to annoy (annoy = -ANYON) criminal (= anagram indicator) (CANYON) down in the valley (CANYON),
2 Remove organ from lounge bar (remove ‘organ’ from ‘lounge bar’ = lueb = BLUE) in Down (down / BLUE),
3 Range (SPECTRUM) of mushrooms (ceps = SPEC-) served up (= reversal indicator) for tea (-T-) from the bar menu (-RUM) (SPECTRUM),
4 List of options (MENU) for university (-U) fellows (MEN-) to begin with (= position indicator) (MENU),
5 Left with poor skin (SPOTTY from opening sweets (opening ‘sweets’ = S-) and nuts (-POTTY) (SPOTTY),
6 Key (music key E-) to new (-N-) and regularly repeated series (-CYLICAL) (ENCYCLICAL) comes from father in Rome (ENCYCLICAL),
7 Small (-S-) friend (pal = -LAP-) trips up (= reversal indicator) in grass (RE-ED) (RELAPSED) and got sick again (RELAPSED),
13 For example, what’s held at military base (PISTOL-GRIP) for flying (= anagram indicator) pilots (pilots = PISTOL-) and force (G- force) from Split (split/tear = -RIP) (PISTOL-GRIP)
14 The overseas (foreign) (the = LA-) weekend (‘week’ end = -K-) in American city (New York = -N-Y) (LANKY) with a tall streak of misery (LANKY),
16 Email inn (email inn = MAINLINE) travelling (= anagram indicator) by Irish Rail from Dublin to Belfast (MAINLINE),
17 Some (ANY-) awful (= anagram indicator) night (night = -THING) (ANYTHING) on a never-ending range (ANYTHING),
19 Not damaged (INTACT) by popular (IN-) diplomacy (-TACT) (INTACT),
21 Ring (O-) where the horses are (-RAC-E-) jumping left (-L-) (ORACLE) – it provides information on the Classics perhaps (ORACLE),
23 Amidst place settings (amidst ‘place settings’ = ACES) for experts (ACES),
24 Banks sales initiative (banks ‘sales initiative’ = SAVE) for Budget (SAVE).