Jeeves didn't consider Mr Wooster's intrusion in his private space in a completely favourable light.
It wasn't proper for the master to spend his time in the servant areas. That was the reason why the separation was there, to divide worlds which need to be divided.
In most houses, even the doors towards the servant areas were different on each side underlying the difference. Jeeves has served in many households till now and in none of them would the master just come to the kitchen and sit down.
Even worse, Mr Wooster went so far to lift his feet on the table.
It wasn't Jeeves' place to teach his master of what is proper and what is not. After all, this was his apartment. There was some comfort in the fact that this was a newly built building so the servant spaces were almost as clean and nice as the main area but still.
In the service rooms, things were useful, not admirable. The space was smaller and it felt like the two of them barely fit in that room.
As a valet who knows his place, Jeeves said nothing but he couldn't restrain his face from showing discomfort before such familiarity. Mr Wooster didn't take notice in that.
That was somewhat strange because he was quick to catch on Jeeves' inner thoughts in other situations.
To bear with those situations Jeeves worked with more focused fierceness doing his task with the proper care. That he did when he was unseen too but then he was less stressed out, his movements were slower.
When he realized that Mr Wooster's behaviour won't stop, that it's probably a part of his character to think that the servant door is just like his own, a passageway that works in both ways, Jeeves started to express himself more vocally. He discovered that when he would summarize his thoughts precisely and honestly that Mr Wooster would leave to go about his business.
Mr Wooster's business would usually consist of visits to the Drone's Club and of trips to the countryside. It was luck that most of the time he ate out because his appetite wasn't much at home. It was as if he was suffering from indigestion.