St Lucia is very different from St Martin but there are places where you can get night life but then retreat to a calm and peaceful environment afterwards. The liveliest places for tourists are around the Rodney Bay area as you have the beachfront strip and Gros Islet which is very lively on a Friday night. There are a couple of complexes with apartment and villas for rent like The Landings right there but if you really want peace and quiet, rent somewhere in the hills a mile or two inland. Marigot Bay is my favourite on St Lucia but not much night life there. There are some seriously upmarket hotels in the Soufriere region and places to rent but the night life is down in the town and not somewhere I'd be like to be.

Have you considered Grenada? Probably my favourite of the larger, English speaking, islands. A very friendly and welcoming Island. Great beach at Grand Anse and a wide variety of accommodation. I spent several months in Grenada while fixing up a boat and had a great time.