Very nice frame. Some comments/ideas on your questions. Just ideas and opinions, mind:
>>8 speed chain - can a Campag one be bought or is an after market one the only option, if so which one works best?
There was a Campag Record in the mid 90s, but for the period of this frame, I think they recommended the Rohloff (http://velobase.com/ViewComponent.aspx? ... &AbsPos=29
). I used them with the early 8 speed Campag index set up, and didn't like them. I went back to Sedis. The current SRAM 8 speed chains are the evolution of the Sedis, and can be had for a good price at many popular retailers (e.g. Chainreaction). They look the part and work well.
>>Possible replacement chain rings. If I can't get originals what are the best for a period look?
8 speed cassette?
The 8 speed rings (without the funny pips and ramps) still come up sometimes on here, lfgss and ebay. Stronglight do good replacements that look OK on the whole. They come up pretty often on ebay. 8 speed cassettes come up pretty frequently, and quite often NOS. Expect to pay about £25 for a good one.
>>Headset, I have the original C Record one that has some pitting on the bearing surfaces and cosmetic marks on the square external edges, will I find better?
If you find one in good condition, you will probably have to pay an arm and a leg for C Record.
>>Saddle, what would look right on this age bike?
Rolls, Turbo, Flite were all common. Others as well. ... All still knocking around. Indurain used a Turbo saddle on his Pinarello, but I think it was already looking a bit old fashioned...
>>Tyres, again what would suit the look of an early 90's bike?
That's just around the time that dual compound and funny colour sidewalls were coming in, IIRC. Early 90s would be gumwall --- Vittoria Open Corsa can still be had in gumwall. My favourites were Michelin HiLite, but you'll struggle to find them in good condition now. Veloflex?
Hope this helps a bit. VeloBase is a good resource if you want to look up the age of different components like saddles. Also pics from races of the time (e.g. Indurain, Rominger, Chiapucci, Bugno)