I live in Spain and I went to get my 11mo dd's ears pierced recently. There's no way I would have done this if I were living in the UK, mainly as I don't see the point. My reasons? All her little friends have them and I think it's important for her to be like all the other little girls, especially since we live in the more traditional southern Spain where you can really feel like an outsider as a foreigner even if you've lived here for years. She'll be different enough from everyone else, what with her foreign parents and her "exotic" name.
I don't want her coming home from school when she's 3 asking why she doesn't have them, or even telling me someone made fun of her because of it. A 3 year old's ears would be much more difficult to care for and she would remember the pain so much more. I was also sick sick sick of hearing "what a lovely little boy" all the time, even when she was in a pink dress! That's not a reason to get your child's ears pierced, but it is nice now that everyone says "what a lovely girl!" at last.
She cried when we got them done, just like when she gets her injections, and it was horrible, but a few mintues later she was pointing at dogs and kids in the park as we walked home. They healed really well and very quickly, she never fiddles with them and they pose no problem at all. They're so tiny you don't really notice them. I've never heard of anyone here having problems, and they mostly leave the hospital with their baby girl's ears pierced. A friend of mine here told me her newborn baby didn't even cry when they did it, and that the pediatrician told her a newborn baby has hardly any cartilage in their ears, so that's why it seems not to hurt, and also that it heals much quicker than in adults.
Of course when I got home from piercing my dd's ears, I read that thread some people have already referred to and burst into tears and called my mum, saying I felt like a shit mum and was going to take them out in the morning. She said don't be silly.
So, after reading this and the other thread, I now know that when I go home to Ireland and wheel my dd around in her pram, a lot of people are going to be thinking I'm a chavvy, cruel, child-abusing, selfish mum. Hey ho. I don't regret my decision at all.
This is really long, sorry! I'm not trying to start an argument about piercing, just recounting my experience, and although most of you won't think much of it, I don't care. OP, what your PIL are doing sounds really annoying - I would have a serious word!