I bought one of these for just £35. It hadn't been used for a few years and cut out when started. The points are hidden in the magneto and impossible to check once you've taken the magneto cover off. I suspected the condenser and took a couple of leads out of the magneto and connected them up to a car condenser (25p from Halfords) and - hey presto - one properly running B120.
These single cylinder two strokes are a bit of an eyesore - pressed steel frame, huge mudguards, enclosed chain and dumpy styling, but the engine's reliable and durable.
Handling is dubious at speeds above 40mph, same old story of poor damping making for elastic band type suspension. The brakes are OK up to 50mph, but try stopping from a flat out 65mph and the forks will twist and bounce and the brake will start to fade - it'll stop working altogether if you use it a few times like that.
Back in the sixties when Brit two strokes were miracles of self destruct engineering there was the B100P, known as the Bloop by owners who were shocked by just how reliable the thing could be. The engine will spit out the small ends or ruin the roller mains at extreme mileages or provocation, but it's so rare that it's not really worth, worrying over. Cycle parts last well. It averages 100mpg which is OK for a two stroke, although there are faster and more economical four stroke singles around.
Spares are easy and cheap to find at breakers. They don't appeal to young learners and are quite hard to sell, so finding one for just fifty quid is relatively easy. Tyre, brake shoe and chain wear are all nominal, so it's very cheap to run. At these low prices it should be possible to buy and run one for a year without significant loss of money. Worth the effort of tracking a good one down.