Refusing to refund

So i needed to replace my driveahaft on my renault clio and i queried it through south peninsula motors, they guaranteed me they could source the part, i paid for the part got it and it wasn't the correct part, after days of struggling hours out of work i decided to get the mechanic to take my old part out to show them exactly how it looks, remember each time i called mechanic I paid for his service in this time i was without driving because it took them over 2 weeks, i then asked my old parts back to put in my car so i could drive as ive been loosing out on work, note im a mobile barber so always need my car, we came to conclusion they couldn't get the part i asked for my refund and my old parts back so my mechanic could fit it, they then lost my cv boots my clips the things they are now requesting for refund they have lost of me the worker said they refunded me but 3 days after i queried it just to find out no refund has been done, when they brought my parts back I asked the guy where my clip was he said i can use that one and only return the shaft, now they speaking of the clips cv boots etc all the tiny bits they know they took off of my own part, All i wanted was my refund and give them the part they knew wasn't the fitting for me, for literally just under 3 weeks. I am forced to pursue this legally