Squeaky belt - 1.9TDi

[steviemac]

Hi all, might be a bit of a strange one ...

I had my local indie do my timing belt, water pump and drive belts back in March of this year, car's been running great since. I've done 9000 miles since then with no incident

Last week we had our first cold morning of the year, started her up and whilst cold I had the classic squeaky fan belt noise, disappeared by the time it warmed up. It's not been quite that cold since so not heard it again

What I've since noticed is that, even when warm, if I turn everything on to load up the alternator (heater, rear screen, radio, head and fog lights, heated seats, etc) the belt starts to squeak a little, but only at idle - give it a rev and it goes

Likewise when applying heavy steering lock whilst almost stationary, eg reverse turn out of a supermarket parking space - it squeaks

Had a look at the belt, and it still seems in good order. Removed the aircon belt to rule that out - wasn't that so refitted it. Pushed down on the tensioner and lifted the belt away from the alternator pulley - only turns one way so not the pulley clutch. It's not a bearing noise, and I've proved it's the belt squeaking with the old trick of pouring water directly onto it when running - the squeak disappears. While running if I push down on the end of the tensioner with a long screwdriver (slackening the belt) the squeak gets worse, but unfortunately I don't have a long slim open-ended 19mm to try it the other way to see if it stops

This only leaves the belt itself, or the tensioner. Had a look on Eurocarparts - my reg no shows an auxiliary belt coded 5PK1432, the belt on the car shows 5PK1435. Having reverse checked elsewhere both belts are listed as suitable for my car - 2003 1.9TDi AVB

I think I'm going to throw a belt on and see how it goes, but am I missing something? Is there something glaringly obvious that I haven't checked?

Thanks in advance for any input