Tom,
i had a similar problem happen to an un-chromed paramount, a 1974 P-15 in "silver mist" paint. The bike was stored in a basement and somehow, rust vapor from elsewhere in the basement became airborne and condensed on the frame - everywhere, even on the aluminum brake calipers, etc. A few (like 5) hours with NEVR-dull got rid of the problem. I hope this is the problem you are having...
If your chrome is actually getting pitted, and if you decide to go with simichrome or NEVR-Dull to try to polish out the rust spots, make sure to use a cloth (like NEVR-dull wadding or terry cloth). The cloth will snag on the rust bubble and will enter a depression caused by the rust bubble and is more likely to empty the pits of rust.
I had some success removing a pea-sized bit of rust from the rear stays of a raleigh international. It took a very long time, but i sanded it down with 1000/2000/nevr-dull, then i used a brush chroming set, then you have to sand and polish it again. The chrome repair was virtualy undetectable - you had to look for it under flourescent lights and you had to know where to look, as the new chrome was just a little bit "warmer" than the original "blue" british chrome.
I'd suggest you might take this approach in the focal-point areas, such as the head tube and lugs, and the seat cluster, than call it a day.
- Don Gillies San Diego, CA, USA
P.S.
http://www.caswellplating.com/
I am currently re-doing the fork crown on a 1974 raleigh pro track bike. This has taken about 3 hours because the pitting atop the crown shoulder is quite deep (i.e. about 1mm deep). You have to get the metal looking as bright and shiny as chrome, before you actually plating it. The plating set will not "fill" any depressions in the chrome, sadly.