I believe that SG Motorsport are the sole supplier for the UK - https://www.sgmotorsport.biz/product/ivans-yamaha-fzs1000-fazer-jet-kit-2001-2002-2003-2004-2005/I think they only advertise the slip-on kit and if you want the full monty kit you need to phone and request it.
As far as I'm aware very few people with the full monty kit and associated intake rubber and airbox mods have replacement headers, just less restrictive end cans and are more than happy with the end result. Whatever you do don't go looking for replacement headers and end up buying the sandyspares or whatever they are calling themselves these days.
Shame about that bike, as I said before if the timing was a bit different I probably would've had it as I bought a fazer just before for 2800 and so far have already spent a grand on bits... I've pm'd you by the way