Vauxhall Corsa engine noisy when idling

Really hard to say without hearing the noise . Could be water pump , alternator , timing chain to name a few .

corsas tend to have issues with timing chain rettles, due to lack of servicing.
chains are internal and are lubricated by the engine oil, if the oil isn't changed regularly, the impurities in the oil prematurely wear the chain and cause it to stretch and hence rattle..

Timing chain already suggested . " the impurities in the oil prematurely wear the chain and cause it to stretch and hence rattle.. " Not the case , any impurities in the oil are caught by the oil filter and rattle is caused by chain wearing and tensioner also and reaching max adjustment