penetrating damp in upstairs bedroom. suspect guttering blocked

Get a survey carried out to ascertain Were the problems are

10 years of gutters never cleaned. classic problem because of gutters not cleaned. you said need the guttering inspected and repaired if necessary, so this is the answer to your question, get a gutter guy to come over and have a look

If the dampness was accompanied by a dusty smell, black mould around windows and the damp wall is an external wall, I would say that you have a problem with internal condensation and nothing else. When it rains the air is full of moisture and this often manifests on the internal side of an external wall. Ventilate more and keep the temperature ambient on colder days.

When it next rains see if there is water coming from the down pipes just above the drains. Get a ladder out and have a look inside the gutter to see if water is flowing satisfactorily. Could be the new gutters were installed incorectly last time and that they might not be large enough to take the volume of water from the main roof or it could be due to position of the gutters. There may b insufficient down pipes or blocked drains in the ground, backing up the pipes. Could b simple solution without incurring more cost ! Damp Smart Mike