could be a sausage ....banger
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not sure about steak .
tbh when i ran our unit we would fit some customer parts but the responsibility was always on the customer. you supply the parts if we strip the car down and they either dont fit, or are wrong ,we inform the customer he gets the right parts, if he cant supply them same day car gets built up as best as and if no room in the garage gets locked up outside until such time as parts arrive.
most folk at this stage would bite the bullet and allow us to supply the parts rather than be without a vehicle. and again if the part they supply fails then they have to stand the warranty whilst sorting out replacement parts.
i found when you sit folk down and explain what may or may not go wrong with the process they dont mind letting you supply the parts.