Scampi's links are good and you won't go too far wrong using them as a starting point, but as noted, bear in mind that the US view on HACCP for juices does differ somewhat to that in Europe - their "Juice HACCP" regulation (21CFR120) is notably more prescriptive than the EU's approach, which largely leaves it up to the processor / Food Business Operator. I've seen at least one FDA "warning letter" issued to a juice processor in Europe that I know well and know they operate to an excellent standard with a HACCP plan that I personally think is very solid, but it didn't comply with the specific requirements of the US regulation.
Nonetheless the US material does have some very useful content, and indeed I cite some of it as a reference in our own HACCP plans for juice products.
Other useful references specifically for the pasteurisation step would be:
https://www.ncbi.nlm...pubmed/11726144 (n.b. "Apple Cider" in the title of this paper is the American term for cloudy apple juice, i.e. non-alcoholic)
This is also useful in a broader sense although goes into soft drinks in general: https://www.research...nd_Fruit_Juices
Have they given you a process flow diagram as the basis for this, or are you supposed to work that out / make one up for yourselves?
I can think of at least one fairly large cider processor (will at least give you a feel for the process) in the Birmingham area and I believe there are a few sites around the Herefordshire region who press apples, so it could be worth reaching out to them to see if they allow student tours or similar, as I always think that it's best to have a rough understanding of the process you're looking at, irrespective of how much knowledge of HACCP you may or may not have.
I'd love to be able to attach some real HACCP plans for you as examples (juice is currently about 75% of my time), but I'm contractually prohibited from doing so!
Nonetheless I am able to spend a small amount of my time assisting students (we had a group of undergrads from an Environmental Health course here a few weeks ago) so if it's useful to talk through with someone based in the UK then please feel free to or send me a direct message.
Having said that, you won't go far wrong with posting ideas etc here for discussion, as there is a massive range of knowledge floating around this forum.