[Arran]

<snip> they do not have to be mica at 455 KC precision ceramic will work fine. </snip>

Arran - just to clarify (for my own knowledge), when you say precision ceramic I assume you mean NP0 or some other tight temperature spec ceramic?  Tube radios get warm... and 'warm' changes the capacitance, albeit to a different degree with different cap types... which is one of the reasons I believe silver mica's are used - because they don't drift much with temperature change... 

I'm inclined to replace silver mica with silver mica, but NP0 ceramics (or equivalent) I believe are ok?  Or the old tubular ceramics?  I did try to find some NP0 caps down here in Hobbit land but they were 500 minimum order quantity... which was about 498 more than I needed.

Stunning radio by the way - we (to the best of my knowledge) never got those down here in NZ... might be something to import one day.

Cheers

Steve

 Both the tubular ceramics (which were used in some slug tuned IF cans originally) and the NPO kind will be fine, but regardless of what you choose they have to be under a 5% tolerance and not drift with temperature changes. Often you can't get a fixed value of fixed cap that exactly equals that of whatever the trimmer cap is dialed to, so you will have to go slightly higher, or slightly lower, or combine two caps to make up the value if it's a really odd value. Outfits like Mouser or DigiKey have search engines that will allow one to find the right kind, and as far as I know you can order whatever quantity you want as long as it's a value they normally stock.
Regards
Arran
Regards
Arran