There is pipework that is used for hot water and also central heating systems that might run outside of the heated parts of the house and are a source of heat loss.
It is a good idea to look at these, and check for good insulation particularly around joints and valves. Remember that improvements to the insulation of this pipework should take in any nearby cold water pipework because insulating the hot pipework could make the cold pipes more likely to freeze in the colder months. London Plumbers can insulate pipework. There is no need to insulate any hot pipework in any of the the living areas unless the heat from the pipework makes a room too hot, cancelling out and the effect of thermostatic radiator valves. If pipework is running the between floors you will only need to insulate these if there is a significant draught where they, because the heat will tend to rise and heat the floor above, fixing the draughts do the same. It is not enough just to insulate any pipework with any old stuff or even the cheaper types of foam pipe insulation, in fact the thicker the better it is, it is also worth investing in good quality material as the extra cost is justified by the gains particularly on the longer pipework runs. A trained Plumber can advise on and carry out heat saving measures in a property. In the ideal world the temperature drop from one end to the other in the pipework should be close to zero. A good result can also be obtained by insulating pipework and then boxing them in wood, ensuring access to the valves. This will give an insulating air gap. There is also lagging bandages, of which there are several types, some of which are covered in reflective foil, but it is normally best to stick to the foamed plastic tubes that are designed for this specific purpose.