I was informed bag and bin was the way to go. I read a Govt website:
You can only dispose of category 2 ABPs by:
incinerating or co-incinerating without processing or with prior processing, when resulting material has to be marked with glyceroltriheptanoate (GTH)
sending them to authorised landfill after processing by pressure sterilisation and marking with GTH
making them into organic fertilisers/ soil improvers, after processing and marking with GTH
composting or anaerobic digestion after processing by pressure sterilisation and marking with GTH (milk, milk products, eggs, egg products, digestive tract content, manure do not need processing, providing no risk of spreading serious transmissible disease)
applying them to land, in the case of manure, digestive tract content, milk, milk products and colostrum, this can be done without processing
using them in composting or anaerobic digestion, if they are materials coming from aquatic animals ensiled
using them as fuel for combustion
using them for manufacture of certain cosmetic products, medical devices and safe industrial or technical uses
I'm not sure what GTH is yet I'm pretty sure I haven't any.
When I buried them I did bury deep and none were dug up. I can understand a few reasons why they wouldn't want us to bury them as there's a lot of domestic chickens these days.