Quick DIY - bathroom lock change

We are trying to do a little DIY/ repairs as we go. Otherwise it could overwhelm us. I think that it is important to "keep" house in good repair. We do not want me be suddenly surprise with "whole" house redecorating. This way it is easier to do.
So we have this simple bathroom lock. Left there from previous owners. It is suppose be brass but over the time is just looks dirty (and I clean it every week).

I finally did something about it and after 5 minutes on E-bay bought nice stainless steel replacement for £2.05 (with free of charge postage too!).
I had a few minutes free while fixing our dinner so I took our screw driver + new lock and did quick removal.

Unfortunately I have found out that under was a scary surprise. Mould!

I scrub it properly and put new lock. I have measured it twice and then screw it in.

Oh, much better. Next time I will have to do a little touch up with paint on the frame. Now we have nice clean and shiny lock and it took just a few minutes.
Dinner almost done and we have still a few of episodes from new Game of Thrones to watch. :-)