The electrical aspects of the installation would need to be done by a "Part P" quallified installer and also "notified". Ask on the electrics UK forum for chapter and verse on that.
As the boiler isn't a new installation, it could be argued that there was no need to add thermostatic rad valves under Part L.
As the boiler isn't a new installation, it could be argued that there was no need to add thermostatic rad valves under Part L.