In all this hot weather had heater on full cold and all doing well till tonight went to move car and when I turned on engine heard strange flapping sound which I located to the heater controls I had left on so turned them off and sound went away turned back on and sound came back.  Car is already having electrical and power steering issues at this rate I may well be getting another car instead of fixing my Fabia.  So please any ideas what is going on and is it cheap to fix.  Thanks.

Might be a leaf or something trapped in the fan?

You may be right does sound only on left side of car if you undo the bonnet when its doing it.  We live in the countryside and with all the combining at the moment dust and grim everywhere so that is possible.  

Yeah, it does happen. It's surprising how much noise it can make.

http://www.briskoda.net/forums/topic/60114-how-to-fix-noisy-fabia-ventilation-fan/

Yup had the same last autumn/winter. Its a horrid sound. Cleared itself up eventually though.

I wish mine was this easy (per my own recent post) but its practically the opposite, quiet on 4, annoying noise more perceivable when on 1 when you barely need the fan at all !!!