From my talks with my pal in germany who does over 60 searches for boar per year the AKAH leather collar are the absolute best available as they have never compomised on quality, but they cost - as always. With leather there is always the getting it wet issue. nylon avoids this.
I think the stuff is already available in Europe so starting up the same business in the UK seems to me not worth it. I would suggest it will be best to go over to the Dortmund jagd & hund exhibition held in feb-march 2013 and see for yourself what is marketed there first before diving in blind.
At the IWA trade show for the two years I did it, there were dozens of pakistani/indian types walking around trying to get our business to make for us the same stuff we were selling but mucheemuchee cheaper they copy existing design but are using low grade leathers and naff brass fittings so the market is pretty well saturated IMHO.
Martin