Confectionary candy and chocolate (hardened) are perfectly alright to carry on your flight. Keep everything neat and packaged, and feel free to pack the sweets in your carry-on or checked bag.
Yes, you may pack food in your carry-on or checked bag, but remember all food must undergo x-ray screening. Foods that are liquids, gels, or aerosols must comply with the 3-1-1 liquids rule. TSA officers make the final decision on whether certain items are permitted into the secured areas of the airport.
You can take them in your hand luggage if you wish but given the amount, placing in your checked bags might be better. Imports to the EU by Cadburys need an Export Health Certificate so no, taking Heroes in is not ok. Their main ingredient is milk. They should be confiscated under the dairy rule.
Merchandise is declared to CBP. If you do not declare something that should have been declared, you risk forfeiting the item. If in doubt, declare it. You are returning from an overseas stay of at least 48 hours.
Can I take chocolate from UK to EU? *Confectionery, chocolate or cakes (including Christmas cake, Simnel cake or cakes containing nuts) are permitted from any country as long as they are for your personal consumption and do not contain fresh cream or high levels of dairy products.
It is important that you declare any food products that you are bringing in from outside the EU. If you are unsure about any of the food products you are bringing in, speak to a Customs Officer in the red channel or on the red point phone.
According to Dublin Airport: Normal food stuffs, such as crisps and chocolate, are fine to bring in your hand baggage. Packs or tubs of butter and margarine are not allowed as they are considered a paste. The guidance from each airline differs. Here's the rules for taking food onboard a Ryanair flight.