My control timer/switch used to switch the pump and boiler on/off; I’ve never noticed the boiler continue to pump after it’s been switched off. I’ve had this solution in place for a few years and the boiler’s been serviced without any problems being reported.
Separating the electricity supply will depend on your set-up. As stated above, my timer (which is now always on) used to control both boiler and pump. I disconnected the boiler lead and added a 13A fuse to it. I hooked the pump power supply (which also has an internal timer control switch) up to a separate 13A plug/socket. So as long as the control timer is on, I can control the pump and boiler via the app or an automated sequence. Hope all that makes sense - it’s a hack, but it works.
I like the idea of replacing the control switch (with a Nest controller) and moving back to my original configuration. ST compatibility may accelerate my plans. Thanks for the info Andy.