Your stat is using the switched live (SL) side of the wiring to switch it on and off, I presume there is a mechanical clock in the front of the boiler to control the time? So in my pic, post #24, section 33, Right hand side is where you stat is wired to just now, which is a 240V switched live.
Do you want to control the pump like the boiler from the thermostat? If so then you'll need to run a neutral and earth from the boiler, or FCU and then take a live from the switching side of the thermostat, usually terminal 3.
Just need to get handy with a voltmeter and check that terminal 3 on the stat is the switched side. When the stat calls for heat it will turn on the boiler and send a switched live to the pump.
I'm sure the SL for the stat should be able to handle to load for the pump, though I'm sure someone here will be able to confirm you can load a pump onto that side of things on the Logic. @ianmcd @DP
Do be careful though, if you're not sure what you're doing then don't as you could cause yourself and the boiler major injury!!