Had a leaking pipe changed the large pipe that runs from the front of the engine to the heater has two branch;s smaller bore since changeing no het getting to car.

It probably a good chance that the system wasnt bled properly and may have an air pocket. when its cold, take the cap off the resevoir and check the level. turn the car on and turn on the heat. allow to idle for a few minutes and carefully check your level again. it might be neccessary to fill the resevoir almost to the top and replace the cap. hold your foot at approxiamately 2000 rpms and see if heat returns. if it still doesnt work, take it back. you should have a warranty. and by all means dont tell them you touched anything.

Possible air in your system you need to bleed air out of your system make sure heater valve is open and radiator cap open when car is cold take all air out and fill as needed

You have an air lock in the engine water jaket and this air lock is stoping hot water reaching the heater, most cars have there heaters above the top of the rad
when you need to do it bleed the air out,,, look for a water hose at the top of the engine its the higest pipe
in this should be a blees screw or a nut with a bolt in it,,,this is the bleed place with a cold engine fill the rad up leave the rad cap off turn on the heater and start the engine up now undo the bleed screw and let the air and water come out till only water is coming out then do this bleed velve up and refill the rad carry on running the engine till it warms up with the heater on the heater should now work and the engine should not over heat