Things to check before you call out an engineer.

Bosch, Indesit all stop working if the filter is blocked. This is located at the bottom usually behind a panel.
Sometimes if the drain hose is connected to a sink spigot, this connection can get blocked.

If they are stopping at odd points during the cycle, check that the hoses are not kinked, both the fill and drain hoses.

Also many modern machines, will not spin if the machine detects the wash load is unbalanced. If for instance you have tried to wash just one heavy towel. This used to be a big problem with Hotpoint machines.

Calgon advertise that you need to use there product to prevent your machine failing due to limescale. Inside the washing powder there IS a Descaling agent. This is why you need to use more if you are in a hard water area. As long as you use the recommended amount of detergent you should not need to use Calgon.

Some people complain about a smell in their washing machine. This can be worse if you use a liquid detergent and / or only use a 40 wash. The answer is every month or so do a maintanence wash. To do this set the machine to a 90 or 60 degree wash with no clothes and the maximum reccommended amount of detergent.

Hope this information helps.......

Ian Foster