Has anyone any knowledge of the planning process that can offer some advice please?

I've live in a semi detached property for the past year. My neighbour was renovating the property when I bought mine and I looked at his plans. Nothing seemed untoward and he had a dressing room planned for against our adjoining bedroom wall.

He has now moved in and has put a en suit bathroom against the adjoining bedroom, not a dressing room. I wouldn't mind but our walls are paper thin and I'm kept awake by his bathroom activities in the middle of the night.

I've tried to talk to him about it but he was quite dismissive of my points. He claims its all been "signed off" by building regs and planning. I don't particularly want to fall out over this but I'm concerned something's not correct.

Should I take this up with the council planning dept. Or should I just buy a good pair of ear plugs?

Thanks in advance