When the only energy source available is electricity, a direct pattern cylinder is the ideal product. The domestic water is "directly" heated by the immersion heaters which sit inside the cylinder. However, the heat-up and recovery times take longer than an indirect cylinder.
Please note - Vented Cylinders are not supplied with an immersion.
Making the decision on the right sort of Cylinder is a key decision. Once you decide that Direct Copper Vented Cylinders give the correct answer then the Telford B3D10545VF is definitely worth putting on your shortlist.