Have a look in the archives for paper reversal recipes Dan.
Really you only need a bleach. If you don't mind handling dichromate then 5% potassium dichromate/5% sulfuric acid should be OK. The dilutions aren't supercritical.
Otherwise it's just developer needed and of course sodium sulfite for the clearing Bath after bleaching.
If dichromates aren't your thing, a permanganate bleach a la ilford film reversal recipe will work, but might be a bit of a stain risk. You'll need a metabisulfite clearing Bath for that.
hth