3dr focuses dont seem to be as bad as 5 door focuses for some reason. I sort of repaired and repainted the wifes focuses rear arches the other weekend. A rear wiper motor wont be dear matey.
Get an intermittent wiper stalk from a focus ghia and fit it to yours. Thats if it doesnt have it already. I also fitted a rear interior light to to the wifes focus. Also I fitted a colour coded grill to hers last weekend tooo.