Had it about 16 months but a call out charge is about £160
Who's call out charge is £160? The current labour charge from the Indesit Company is around £105. When you phone them they do however route you through an insurance/maintenance contract spiel and make it appear as though it is compulsory. It is not and if you insist they will do it for the rather high labour charge only.
A local independent would be far less expensive on labour charges.
What you describe is an unusual/illogical fault. This machine is now almost 100% Indesit. It has some of the most unreliable electronics on the current market.
The first thing to do is to see if it has a pump filter behind the kick strip at the front. If there is a filter there then you need to remove it and check for any obstructions.
If it is clear and you have access to a megger or suitable multimeter and know how to use one it would be worth removing the mains plug and testing the heater for low insulation.
Failing that try our 'find an engineer' link at the bottom of this post to see if we have someone in your area who can help.
That which can be asserted without evidence, can be dismissed without evidence.