I also like the Empire Strikes Back pinball... It's gotta be the best of the Hankin pinballs!
Right now we have 2 Hankin pinballs in the workshop... Orbit 1 and Shark - both getting full reco's.
Thankfully they're quite easy to work on - comparable to Bally's of the time. But, as Hankin made their own mechanical parts, it can be difficult to keep it original if you want to keep it working.
Hope all goes well for you Dean.
PS: We do have ALL of the Hankin pinball manuals here, so if you do need a copy and Nick can't help, let me know.