3 guesses each to begin with.

1 MADE FOR SHARING. QUALITY STREET - ApusApus
2 CHOCOLATE, WITH A FIGURE LIKE YOURS? MALTESERS - ApusApus
3 ONLY THE BEST IS GOOD ENOUGH. MILKY BAR - Ramone
4 BUY SOME FOR LULU. SMARTIES - jagwheels
5 AND ALL BECAUSE THE LADY LOVES…….. MILK TRAY - Flossie & Lincoln
6 FULL OF EASTERN PROMISE. TURKISH DELIGHT - Flossie
7 THEY GROW ON YOU. ROSES - Cactuslil
8 FOR ADULTS ONLY. BOURNEVILLE - ApusApus
9 TAP IT TO UNWRAP IT. CHOCOLATE ORANGE - Oxfordboy
10 WHAT’S GOT A HAZELNUT IN EVERY BITE? TOPIC - trevnhil
11 GET THAT FRIDAY FEELING EVERY DAY OF THE WEEK. CRUNCHIE - Cactuslil
12 HAVE A BREAK, HAVE A …….. KIT KAT - Lofos-5
13 BRIDGE THAT GAP WITH …… SNACK - trevnhil
14 HELPS YOU WORK, REST AND PLAY. MARS - trevnhil
15 A BOX OF CHOCOLATES IN A BAG. - REVELS - jagwheels
16 NUTS, WHOLE HAZELNUTS …… WHOLE NUT - Oxfordboy
17 WHO KNOWS THE SECRET OF THE …………. BOX? BLACK MAGIC - Oxfordboy
18 THEY CAME IN SEARCH OF PARADISE. BOUNTY - ApusApus & jagwheels
19 DO YOU LOVE ANYONE ENOUGH TO GIVE THEM YOUR
LAST ONE? ROLO - Lofos-5 & Lincoln
20 A GLASS AND A HALF OF FULL CREAM MILK IN EVERY
HALF POUND. DAIRY MILK CDM - Cactuslil
21 THE SWEET YOU CAN EAT BETWEEN MEALS WITHOUT
SPOILING YOUR APPETITE. MILKY WAY - Cactuslil
22 ONLY THE CRUMBLIEST, FLAKIEST CHOCOLATE. FLAKE - Flossie & Lincoln
23 MELTS IN YOUR MOUTH NOT IN YOUR HAND. M&M's - Lofos-5
24 THE THREE COURSE SNACK. TWIX - ApusApus
25 GET ON BOARD. DOUBLE DECKER - Trevnhil (Trev's answer was probably a typo)