The correct way of wiring for a negative earth ignition is:
1) 12V via ignition switch and fuse to coil +
2) Coil - and condenser to contact breaker
3) Contact breaker body and distributor body connnected to battery - via chasis

Measure coil resistance from + to - and from output to - with all other wires disconnected. Resistance from + to output should be the sum of other 2 measurements. Condenser should have infinate high resistance. You need a special capacitance meeter to measure the value of a condenser, and it is too expensive for most people to buy.

Condensers are of low quality and supplied with wide tolerances (20%). It is made up of layers of foil interleaved with layers of dialectric material, and can also break down at high voltage (even more expensive to measure/test). Make sure that the body of the condenser is screwed down properly to the chasis (measure resistance to battery negative terminal). It can also be that there is no or little power getting to the coil while the starter motor is turning. Starting is assisted by the alternator/generator, which might also be causing the problem (e.g. bad connection causing voltage drop)?.

Go about it systematically, starting with the smalles building block of the system. When checking the ignition, keep in mind the spark occurs when the contact breaker opens. With the ignition to "on" you should see a spark on the contact breaker if you turn the engine with a spanner on the crank shaft. If there is no spark as the contact opens, then it is either 12V, coil, condenser, or bad connection/short on any of these. If there is a spark, then you should also get a spark on the coil output lead. If there is a spark, then you should also be able to get a spark on the spark plugs. If there is a spark, then you shoudl be able to push-start the car (and the BW35 can also be push-started!). If you can push-start it, then you should be able to start it with the ignition key.

Concerning cap and rotor, the breakdown voltage of air is theoretically 3kV per millimeter. So a good ignition that generates 30kV can make a 10mm (0.4") spark (in air). Usually a fairly new cap and rotor will not be the problem, unless it has a rev limiter in the rotor (like my 240) that got stuck/broken.

Have fun...