Assalamo Alaikum Wr Wb!
Dear @marsadvice,
The following varieties of chocolates from Mars Chocolates are certified by the HFA in the UK:

• Galaxy SmoothGalaxy DarkMars   – all variants (Standard, white & Almond)Snickers –  all variantsMilky way – all variants
• Topic – all variants
• Flyte – all variants
• Bounty -all variants (Milk & Dark)
• Ripple – all variants
• Minstrels – all variants
• Revels – all variants
• Maltesers- (Milk & White ) all variants
• Counters – all variants
• Tracker –  all variants Choc Chip, Nut, Raisin)
• Galaxy Flutes  all variants (AKA -Dove Flutes, Galaxy Amicelli Chocolate)
• Milky way Crispy Rolls –  all variants (AKA Milky Way Crispy Rolls Ameo, Galaxy Amicelli Vanilla)
• Mars Delight – all variants (AKA Delight by Mars, Delight De Mars, Dove Senzi) all variants
• Amicelli all variants and names as above, also
• Amicelli Speculatius limited Edition (AKA Amicelli Wintergenuss)
• Amicelli Cappuccino all variants
• Amicelli Tiramisu
• Twix Fino
• Celebrations
• Twix, Twix  Reduced Sugar
• Balisto – only the following variants (Woodberry, Corn Mix, Musli,Strawberry, Wildberry)
• Mars Planets
• Snickers Cruncher
• Twix® Ice Cream Bar
• Snickers® Ice Cream and all variants (Stick, Bar and Almond Bar)
• Mars® Ice Cream and all variants (Stick, Milk Chocolate coating salted caramel Bar, Dark chocolate coating caramel Bar and Milk Chocolate coating caramel Bar)
• Maltesers® Ice Cream Stick
• Galaxy/Dove® Ice Cream Bar and all variants (Heart Vanilla Bar, Heart Chocolate Bar, Choco Heart Caramel Bar, Triple Choco Stick, Milk Stick and Almonds Stick)
• Galaxy® Ice Cream and all variants (Swirl Caramel Stick and Vanilla Bar)  
• and
• Milk Way® Ice Cream Bar

The only question would be if you trust the certification of Halal Food Authority UK.
As always the best advice would be “if in doubt, leave it out!”
And only Allah knows best!
Ma’assalam,