WildAtlanticWay, oh a Bernina 830 machine brilliant. This was the one machine that Bernina got totally right, hence it attracts high prices. Oh this will be so exciting for you - good luck.
With regards to any extra feet/accessories may I recommend Bernina (Bogood's) own parts place which is down in Cardiff, they have many feet and accessories for old machines and will certainly be able to help you, however even these old style feet cost quite a lot. By the way the ladies at Cardiff are extremely knowledgeable and will help you no end. The phone number is 029 2079 2079.
I can let you have details of the feet that actually came with the machine, and by the way if you can get hold of a manual it is laid out well and so easy to follow. I would recommend that if you have this machine well worth getting this serviced - after all this was a top of the range machine back in its time, and you will notice that it 'purrs' along nicely afterwards. Only use the specific Bernina bobbins on this machine they are metal.
I was looking at Helen Howes' site over the weekend, and she has/had some older Bernina feet, including the little black gadget that is used to unscrew the needle screw.
If I can help any more, just ask - I am always in need for a distraction as you well know.