It may be an idea to go directly to the Industry recognised body if you`ll pardon the pun

Lois Further to ptaylor's advice there are a number of trade organisations (bodies!) representing undertakers/funeral directors in the UK. There's probably also at least one for the various firms which manufacture coffins. (Your post reminds me of a visit to a coffin factory during my time with HSE in the 1980s - it was slightly spooky seeing numerous coffins of different sizes in the workshops and storerooms. I was also enlightened about kerfing as an important technique in making a coffin.) If you are also looking at burial and cremation there are plenty of OS&H aspects to include, and almost certainly more than one national organisation involved judging from the different journals which my late (!) employer's bereavement services manager had in his office. Dealing with dead bodies is effectively a major UK industry and, by its nature, is unlikely to be hit by recessions or lost like manufacturing industries to overseas competition! in addition to looking at available literature and contacting national bodies it would be worthwhile if you haven't already done so to contact several undertakers and a coffin manufacturer to explain your quest and ask if you could visit them for a chat and look at what goes on. Some might politely decline your request but others may well say yes! Judging from the number of TV documentaries in recent years about the work of undertakers, coroners, etc., it seems that some people in the industry don't mind outsiders knowing what their work involves.