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
Falcon Raptor (FN12) Lighthunter - Walnut FX Cutlas - EB XVI - HW35 'Karbine' - BSA Airsporter MK4 - Webley Mk III - Relum Tornado - FWB Sport 127 Deluxe - Crosman 1322 custom - Sussex Armoury Jackal - BSA Superstar - Logun Eagle (All .22) and HW80 in .25