Firstly, thanks to Amalfi Girl for giving me the information that enabled my partner and I to make an informed decision and take a great trip.
SORRENTO TO PAESTUM:
We caught the ferry from Sorrento at 7.30am on a Sunday. Although a large ferry, we were the only 2 people on board. It bypassed Positano and only picked up three passengers at Amalfi. Next stop Salerno, arriving at 9.10am.
Caught the train to Paestum, which took 30 minutes (as advised by Amalfigirl).
THE BEST BITS, (although it was all excellent):
1)Fantastic views of the entire Amalfi Coast from the ferry.
2)Paestum is alongside a small villge with a nice, relaxed feel. Although there are shops and restaurants catering to the tourists, they absolutely do not hassle you and the prices are normal. (Unlike Pompei which reminded me of Egypt as you leave the train station and charge 4 Euro's for a can of coke and a plastic cup).
3)The sight itself is a lot bigger than we had imagined with one of the most awesome Roman Temples that we have seen, (which reminded me of the Acopolis in Athens). There are two further impressive temples as well.
4)As the area is so large, with many Roman buildings and shops, visitors were spread out and thin on the ground.
5) Salerno is a typical large Italian town with no tourists and a real local feel. It has a huge promenade with green areas and palm trees, fronting a beach. This is a great place to get away from the hustle and bustle of a holiday destination such as the Sorrento Peninsula with it's huge amount of visitors and mingle with purely local people.
NEED TO KNOW:
1)The ferry docks at the opposite end of town to the train station. We ambled along at a casual pace and by chance got to the station at exactly the departure time but luckily the train was 5 minutes late. On a Sunday, it should leave at 9.42am and the next train is at 12.15. Therefore, do not hang about if you want to go straight Paestum. (We felt that although we wanted to visit Salerno as well, getting to Paestum at 12.45 would not have been an efficient use of our available time).
2) The last ferry back to Sorrento leaves at 5.50pm, DO NOT BE LATE otherwise you will have a long journey back either via various buses or trains via Naples.
3) The return ferry was fairly quiet from Salerno but packed from Amalfi, therefore make sure that you are sitting in the prime viewing seats before then as everyone heads straight for them. (i.e. outside on the side facing the coast).
Ferry; 21 euro return.
Train; 10 euro return.
Entrance; 5 euro.
Museum; 1.5 euro.
FINALLY: Allow up to two hours at Paestum plus 45 minutes for the museum if you like to see everything at this type of sight. Allow additional time if you stay for lunch.
Times of trains may be different on a week day and the ferry may also be busier on a week day (but we wouldn't know for sure).