Alec proved to be one of the best and most professional service persons I have dealt with in over 40 years in London. We needed to replace two boilers: one in a small flat, and a second in a very complex domestic heating and water set up in a detached house. From the first contact, he is a total professional: punctual to the minute for all appointments, totally straight forward with information, open minded as to solutions for the problem at hand, concerned about cost and ecological considerations with choices to be made. His quotes were very competitive (and half the price quoted by British Gas), and he suggested the most efficient boiler in each case. A Vaillant for the flat and a Viessman for the house. His explanations of the cost benefits of an outdoor temperature sensor of the Viessman were accompanied by his sending many pdfs explaining how this system worked. Alec and Marco proved to be a very reliable and thorough work team, to the extent that they do not leave the job until every aspect of the installation has been checked. They also leave the site totally cleared of mess and rubble. The benefits of the Viessman were apparent on the first day: for the first time ever, I now live in a space which is permanently at a comfortable temperature, night and day, and with the promise of a reduction of 20% in gas bills due to the alternate technology offered by the Viessman system.