I’ve done a lot of reading up on the alarm, and been told by the dealer it’s impossible to fit. I quote the sales guy when he said "HD haven’t invented a cable capable of connecting the alarm to the siren". He went quiet and mumbled when I pointed out "the un-invented cables was on sale on their own website for £34". I ended up reporting this to the dealer principle and getting one fitted for free.
For anyone interested. Parts required are as follows.
69202993 siren adapter wire
69000124 alarm siren
Fitting instructions
Ive not fitted one but it looks easy enough with basic tool and bare minimum of mechanical no how.
I was getting stone walled by the dealer until I hit them with part numbers and fitting instructions. They folded pretty quickly after. I hope it’s just lack of knowledge on their part, as in excusable as that is. The alternative is their actively trying to rip people off.