Small Job For A Builder / Tradesman

[Dublin2BuenosAires]

I have an old aircon unit built into the wall of the bedroom in our apartment, it's about 60cm * 50cm and needs to be removed as in winter cold air blows straight through it and hot air comes in from outside in the summer. I need it removed, which I could have a go at, and then need to fill the hole in the wall, which i suspect I would not make a good job of.

The aircon has been replaced by a modern version so nothing more than removing it is required.

Any recommendations for someone to fill hole I'd be making in the wall?