I had my halstead combi boiler fitted about 2 years ago. I have never had a problem with it until now. I have got central heating but I have got no hot water. When you run the tap it is cold then it goes hot for a few seconds. After that it then runs cold.
Please can you help me to solve this problem. Thank you

You could have a defective mixing valve/tempering valve. This is best left to a professional who has the skill to repair. The valves are expensive and if it can be cleaned and put back in service you will be $$$$ ahead.