Welcome aboard *welcome*and a great model to have as well, we all are a nosey lot so more info in the relavant board about yourself ,where you are based , there are some much more knowledgeable people here than me always willing to help but heres my tupennce worth,
whats wrong with black ?
The clutch on the plungers is in a sealed dome within the chaincase and is probably BSA's best offering however it runs dry so if oil is in there could be contaminated as you think ,best pull it down for a look.
your bike should I think have the "cowpat" type cowl if you search for it you'll see versions on here.
That brake ,i think is the 8" single sided and set up right is pretty damn good , post us some pictures ,may be rusted from standing ,cable stretched, actuating arm in the wrong position ,should be making firm contact just before 90d or linnings worn etc but defo can be sorted, keep at it ,you'll love her, cheers Bob