Don’t be afraid to buy used parts from a salvage yard. Control arms and wheels don’t wear out. If the strut is bent, a new one may be in order as those do wear out over time.
The wheel arch is the rounded part of the fender in back, in front, and over the top of the tire and wheel. If the distance behind the inflated tires is the same on both sides, then the probability of the control arm and/or strut being bent is considerably less. You can measure it by sticking your fingers between the tire and the back side of the tire on each side.
I have never seen a Citroen Picasso. In fact it has been years since I’ve seen a Citroen in this country. They are no longer imported to the USA. https://www.google.com/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1454&bih=704&q=citroen+picasso&oq=citroen+picasso&gs_l=img.1.0.0l10.1356.6164.0.9418.15.9.0.6.6.0.107.832.7j2.9.0...0.0...1ac.1.6.img.-2byJl3JzxI#imgrc=zltZPz0N_odV7M%3A%3BzmGoOel9JSCrBM%3Bhttp%3A%2F%2Fswotti.starmedia.com%2Ftmp%2Fswotti%2FcacheY2L0CM9LBIB4C2FYYSBWAWNHC3NV%2Fimgcitroen%2520xsara%2520picasso3.jpg%3Bhttp%3A%2F%2Fswotti.starmedia.com%2Fcars%2Fcitroen-xsara-picasso_37070.htm%3B1024%3B721 It looks like a nice little car.