As you correctly say Viv the ad could be for anywhere, the only major business in Hampton Street was Wheelers Timber Merchants from around 1932 to 1955 and they were across the road from No. 5.
Having had a rethink (on what you said), I now think it says Top line SCRAP, Middle line CARS, Bottom line CHURCH Rd.
I think the whole sign was probably for Taronis on Aston Church Road and probably says SCRAP METAL & CARS, ASTON CHURCH Rd.
Of course this is only the latest sign there are others underneath which are illegible and will remain that way unfortunately.