Well in 43 years my Norton has always been oil tight if I do get a drip it be from using the oil drain washer to many times, it has had its share of speeges but I fix them straight away and had a blown head gasket once, my old 81 Triumph Thunderbird brought new never leaked oil in the 9 year I had it and I had done 250,000 ks on it.
I like to keep my oil in my motors, all my engine cases are oil tight and have always been since I brought my Norton new, so yes you can have a British bike that don't leak oil, even the 79 Bonnie I brought off my brother in law that every time I rode it something would fu.. up but it never leaked oil.
My Norton might be showing its age, looks ratty and rought around the edges but she don't leak oil, Al maybe you need to talk to your bike more often.
Ashley