These boilers have several names "open vented, vented, conventional, and regular or heat only". Your existing boiler will most likely be a regular boiler with external controls consisting circulating pump, diverter valve, two channel programmer, and room and hot water thermostat; they are very flexible and can be fitted to most arrangements of systems e.g. whether the primary (the water that runs around the boiler) is vented (there will be a small header tank in the loft area) as shown in the illustration below.
Or unvented which means the primary water is sealed under about 1-1.5 bar of pressure, there is no header tank in the loft area but there will have to be an expansion vessel with a safety release valve to take up the expansion and contraction.