Thank you for all your replies.
From what I've subsequently read, nocturnal funerals in the early 17th Century were conducted at the behest of the wealthier classes, and done for a number of reasons;
1. Privacy. Churches were public places, where anyone could attend a funeral if they felt like it. A nocturnal funeral avoided crowds of gawpers, and allowed the family to mourn in private.
2. Cheaper. The wealthy (as these burials seem to be) were expected to commission a public sermon and distribute alms to the poor at a funeral. But if it was at night, then there was likely to be fewer people about who would need to be entertained or given money to.
3. Avoidance of pomp and taxes. If a person's family held arms, then the College of Heralds could dictate the funeral proceedings and trappings, and then claim a fee for doing so, and for displaying the said coats of arms. Nocturnal funerals were a way around this [I'm not altogether sure how, though!]
3. Fashion. There was an increased interest in the ancient customs of the Romans, and night time funerals were supposedly one of them. So to be buried at night reflected your higher cultural leanings.
4. Poetry. The necessary torchlight and solemn appearance at a nocturnal funeral was meant to heighten awareness of the mortality of man.
5. Splendour. In converse to no.1,2 & 3, a nocturnal funeral could be used to emphasis the wealth and splendour of the deceased (whilst still being cheaper). A funeral procession with scores of burning torches and solemn mourners, passing through town at the dead of night could be quite a thrilling show.
6. Speed. With less need for a sermon, or to follow the dictates of the Heralds, nocturnal funerals were easier and quicker to organize.