In this pic, see the rubber hose on the left that goes from the radiator to the engine? The pipe that rubber hose goes on is the thermostat housing and you need the cambelt off to remove it. Yes it's a very poor design!
Nope, the alternator belt is the one you can see going round the pulleys on the far left of the engine. The cam belt (aka timing belt) is behind the plastic covers, this is what connects the crankshaft and the camshaft together to turn at the right speed at the right time to open and close the valves.
ok doky. tried to do t/belt wen i first got car. my m8 said he couldnt as some tensioner wouldnt move and he didnt wanna bust it till i got a replacement tensioner, t/belt hangin up in my shed at mo, can i get belt off and bak on with out bustin tensioner
Don't know what year yours is, but have found a few with also a idler pulley, unless my old age is fooling me and that was the mk2 astra I had!!
If doing a stat I would do a water pump at same time, cheap enough around £15, and stops all the hassle if it goes and starts leaking 5 minutes after doing the belt.
I always do a nerw stat and pump at same time as timing belt, ie every 3 years.