Hi Will,

I was on the hunt for parts when I refurbished my SA Woodstock earlier this year and found out that Julian Bond has a pretty good stock http://www.airarmsspares.com/air-arms-spares/ you want anything with AR before the number on the stock code (might be worth looking at the diagram on chambers)

If he's no help, I know Manchester Airguns has a 'tub of bits' that certainly has Jackal trigger parts in but think they are mainly Air Arms which are slightly different.

Hope this helps

Chris