Well done, that didn't take you long, even with running a new cable.
The boiler cycling is normal. As you suspect, it will be regulating the temperature of the water leaving it to maintain the temperature selected on the boiler thermostat, otherwise if it kept running, because boilers are always sized in excess of the system they are connected to, it would actually boil the water. This should have been the case before you converted it to a C Plan.
When just the hot water is on, the boiler will probably be off for extended periods of time because it can take quite a while for the hot water it has generated to circulate around the hot water cylinder by natural circulation.
When the radiators are first started and the system is cold it will run for longer periods, however as the system, and your home warms up the on periods will get shorter and the off periods get longer.
How can you check the pump is running? there are several ways, you can usually hear it if you put your ear close to it and feel a slight vibration if you touch it. Best to do this when it's cold though. If you are there when it starts you can usually hear it 'kick in'. If you can get someone else to switch the heating on while you stay with the pump you may hear / feel it. However, there is a more obvious way. The radiators won't get hot if the pump isn't running.
I'm not sure how the Evohome sensors actually work, but I imagine that relay will stay energised until all of the Evohome thermostats are at their set temperature. Once they are all up to temperature, the relay should de-energise.
Can't help with the Evohome senors I'm afraid, I've never personally done that bit because they don't have any wires attached