Welcome Nicola. Your machine is probably a BZ35 (ie not sure if there is a Bezzera VZ35)
It's a bit hard to say what the problem is based on the info provided.
Have you had this machine for a while working correctly but has only recently shown a drop in temp?
If recently acquired, how long are you letting the machine warm up for before trying to make coffee? While the boil may reach heat fairly quickly, you need at a fair bit more time for the group head to warm up.
It could need adjustment but need to eliminate other factors first.