On the back of the timer there should be a connection diagram.
Check yours to see if there is one.
Before you start messing about with stuff switch off the power to the boiler, otherwise you may get zapped with 240v.
Now, quite possibly the wires are:-
Wires 1+2 are the power supply to the timer, 240v.
If there is a diagram, there will be a small circle with the letter "M"
Don't link these out, just leave them on the timer.
These wires may also be coloured, brown and blue.
Wires 3+5 are the ones you want to link out.
These have female spade terminals attached, once they are removed from the timer, they should be able to interconnect with each other, perhaps using some insulating tape to ensure they are in good contact with each other.
These wires should(?) be the black ones.
The diagram on the back of the timer should be showing a switch contact between these two wires.
BUT before you do anything on yours, check the diagram.
Upon switching the power back on, the CH should come on. Keep fingers etc away from the live connections on the back of the timer and make sure they are not touching anything that will conduct.
Not sure the voltage on the switch terminals.