When returning from Alicante, study the timetable carefully as the last train at night only goes as far as Altea and you have no connecting train to take you to Denia. The last train arrives into Denia at around 22.15pm. It makes me wonder why trains aren't like this in the UK. From what I remember, trains and stations are old, scruffy and often unsafe places to be. They're also considerably more expensive. The train on the Costa Blanca is a wonderful way to get around and without doubt, the best way to see Alicante.
Train journey times Denia to Benidorm on L9 - 1 hour 17 minutes Benidorm to Alicante Mercado on L1 - 1 hour 14 minutes Total journey time = 2 hours 31 minutes