Just looked at a 5 to purchase (1997 1.8), its really nice apart from on start up and on tick over the tappets were very noisy. I havent taken it for a drive yet so the car wasnt warm and had been sitting on the forecourt for a couple of months, its pretty damned cold today too! Oil looks clean.
I vaguely remember this being quite common but cant remember whether to be concerned or not
I have a 1997 1.8 as well and this is a very common sound. Search for “hydrailic lifters” or “HLA” and you will find loads. Basically the oil has gunked up around the lifters (tappets) hence the noise. Usual with standing idle and old oil. I get it on mine as it is a weekend car. A good fast drive will reduce it but the best way is to change the oil with a good quality one after using an engine flush such as Wynns that help clear some of the muck out.
Some stuff here, in FAQ