Having studied the Haynes Manual and elsawin, it doesn't look to difficult (especially compared to an Alfa V6...)
I'll try to get some photos when I do it.
Does Altea have the big or little engine support at cambelt end.
JT - unfortunately you just can't tell what condition a cambelt is in by looking at, on or off the engine. So many engines go bang because the cambelt "looked" ok.
if you've ever tried turning a camshaft, you'll know how much strain that belt (and the tensioners/pulleys) is under!