Across:
8 Posed (SAT) for most of (y) those overseas (“navy” without “y” = NAV-) (SAT NAV) – it’s the talk of the town on TripAdvisor (SAT NAV),
9 Relieved (-EASED) after (= positional indicator) last month (December = DEC-) (DECEASED) passed (DECEASED),
10 Ned is not in the West End (“Ned” is not in the “West End” = west = STEW) for the dinner (STEW),
11 Just painted (wet = -TEW-) up (= reversal indicator) job centre (‘job’ centre = -O-) in Ulster (NO-RTH-) and, yes (-Y) (NOTEWORTHY), it’s significant (NOTEWORTHY),
12 Turns up (= reversal indicator), one (-I-) going to pot (pot = -TOP-) in Australia (AU = U-A) (UTOPIA) paradise (UTOPIA),
14 Search is (search is = CASHIERS) off (= anagram indicator) – they’re found at the bank! (CASHIERS),
15 Chart (GRAPH-) Third Reich (Third ‘Reich’ = -I-) from first of the camps (first of the ‘camps’ = -C) to architect (DESIGNER) (GRAPHIC DESIGNER) responsible for the visual impact (GRAPHIC DESIGNER),
18 Function for astronomer (STARGAZE), Trim (t) pioneer (‘start’ without ‘t’ = STAR-) and peer (-GAZE) (STARGAZE),
20 Sacramento disregards scam? (‘Sacramento’ disregards ‘scam’ = raento = ORNATE) Fancy that! (ORNATE),
22 Level (FLOOR) the surfer is on (surfer is on surf -BOARD) (FLOORBOARD) tends to be creaky if it’s not nailed properly (FLOORBOARD),
24 Half of 17 down (‘snowdrop’ = DROP) stop discussing it (DROP it),
25 Altogether sounded like one (IN UNISON) popular (IN), small place of learning (UNI-) for one of those in Trinity (-SON is in The Holy Trinity) (IN UNISON),
26 Amuse (OCCUPY) copper (-CU-) mentioned in rewritten (= anagram indicator) copy (copy = OC-PY) (OCCUPY).
Down:
1 Irishman (PA- -T) admits it’s (its = -ST I-) kicked back (= reversal indicator) (PAST IT) over The Hill (over the hill = PAST IT),
2 Last Christmas (last “Christmas” = S-) present (-NOW) (SNOW) of a winter blanket (SNOW),
3 School (S-) doctor (= anagram indicator) leaving (leaving = -VENGALI) (SVENGALI) with sinister controller (SVENGALI),
4 Cut out (EDIT) bad (= anagram indicator) diet (diet = EDIT),
5 Gives threatening looks (SCOWLS) to beasty type (-COW-) left (-L-) in ship (S-S) (SCOWLS),
6 Enjoying The Affair without the wife (CARRYING ON) making a fuss (CARRYING ON),
7 Note (“see” = “sea” = SEA) report (= homophone indicator) by Arabian (HORSE) (SEA HORSE) looks fishy (SEA HORSE),
13 Test (PAPER) series (ROUND) (PAPER ROUND) delivers on its promise of the sun (PAPER ROUND delivers on its promise of The Sun),
14 Beg (CADGE) Stringer to leave greeting cards (‘stringer’ leaving ‘greeting cards’ = gecad = CADGE),
16 Sounds like a stone in one’s wheel cap (RATTLING) is worrying (RATTLING),
17 Donors (donors = SNO-DRO-) freely (= anagram indicator) welcome work (-W-) at park (-P-) (SNOWDROP) in the spring garden (SNOWDROP),
19 Lie in wait (AMBUSH) for early morning (AM-) transport (-BUS-) with heroin (-H) (AMBUSH),
21 In retrospect (= reversal indicator), there’s nothing (-O-) in competitive games (sport = TRO-PS) (TROOPS) for boy-scout groups (TROOPS),
23 Play truant, partly missing (‘play truant’ missing ‘partly’ = uant = AUNT) with older relative (AUNT),
24 Donald (Donald DUCK) is out for nothing in particular (cricket batsman’s score of nought = DUCK).