I put my Puma up for sale on ebay this morning and then according to sod's law, the fucking thing shit itself on the way to work 5 minutes later

i was going up through 3rd gear and suddenly heard a noise like stripping teeth and i thought the cam belt had gone but the engine stayed running and wasn't particularly noisy or anything. i checked for FEAD belt, but that was all still there.

it idles ok and drives ok on light throttle up to 3000rpm or hard throttle at higher revs, although down on power. i'm thinking it might be something to do wit hthe variable cam timing, but have no idea about them and don't have a haynes manual to read up. i was going to take the cam cover off the top and have a look what i can see, but anyone else got any ideas or experience of similar things?