Hi, thanks for the reply. The thing is that I dont have any symptoms atm - no loss of power, around 45mpg round town. Last week it made a sort of whining noise while cold and a burnt smell from under the bonnet but was only for 2 days and then it stopped. Serpentine belt looks nice and tight. Tensioner looks like is working well. Mechanic said it might be the alternator coming close to a service. To be on the safe side i did an oil change yesterday, replacing the semi-synthetic (supposedly ford-safe) oil another garage had put in it 3000miles ago for full-synthetic oil Total oil.
By the way, I was also delighted to find that it is much easier to change than in my previous 2003 corolla 1.4 vvti.