Stay well clear of Buy Parts By, they only seem to sell inferior parts. If you want an exhaust that will probably rust up as soon as a splash of water touches it go for it, if you want a quality part dont.
I have just bought some front wishbones off them after advice on here. I put them on the car and as soon as the car was on the ground the upper wishbones shattered!!!! They are now refusing to refund for all of the parts even though they werent ever really used. Disgusting if you ask me and I would stay well clear. I am currently waiting on the other parts to come back from a friend who is stress testing the rest of the wishbones, to see if the lowers were as poor quality as the uppers.
I got a back box for my 147 from Euro Car Parts, the part is good quality and at a very good price. Only £40.