Well, all you have to do is go to google and type in 55kg in lbs or 55kg in stones and you will get the equivalent. You live in gibraltar so when you go shopping what do you pay in, pounds? What if you cross over to spain? Spaniards don't use pounds, they use euros! So how do you know how many pounds to give them? you go to a currency exchange house and they do the exchange for you. So for 1 pound they will give you around 1.26 euros, and the rate varies. The only diference is that for kgs in lbs and stones---the scale never changes. 1kg=2.2lbs and 1 stone=6.35kg or 1 stone = 14 lbs!
Now, you live in europe and the perceptions over there are different. I can tell you that when my european female friends come to the usa, the first thing they notice is that gals here are a lot heavier than in europe. When they go shopping, even though they have the right size, the sizes are too large for them. So how much should you weight? That depends on you, and how you feel about your body; however, if you ask people they will all tell you different. In the usa they will tell you that you're average for your height and weight, while if you were in italy, and even france they will tell you that you're overweight for your height and weight.