hi MickC, i assume from what you say that you intend to apply for a grant towards the ap? personnally i cant help with that but i am sure there will be others along who can.
as to the next part regarding the kit you need/would like then yes its a labourious task.
the motability search tool will narrow down by fuel,size,vehicle type,gearbox etc but then its a case of making a short list and trawling through the manufacturers site to find the nitty gritty of whats included whats in a pack and whats available as an extra. i think you need to do this before applying for the grant as i think you need to know the ap your looking at and you need to be able to say why particular models are on your list and i think mota can come back with other usually cheaper options.
watch out for the packs many manufacturers have started putting desirable things like heated seats etc in packs along with other stuff you may not need or want at silly prices. it does make producing a like for like short list very tricky.
but good luck and if you get stuck just ask theres loads of knowledge on here and they are happy to help.