Main water pipes

Thats a long length of tube

Does the engine end of the heater tube attach to one side of the oil exchanger ?

....meant to go on to say, was there a revised type of tube fitted to later cars? I recall someone looking at mine and muttering it had black coloured tubes instead of some other colour which was good apparently

Sounds like an urban myth to me .....pipes is pipes ....I've got black ones and they go up to 11