Many thanks indeed for your helpful reply, Arthur!
Your pointing out that the term 'restaurant' would be unlikely to appear on the 1841 census prompted me to scrutinise again the barely legible handwriting on the copy that I have of the relevant page, and it does in fact appear to say "At side of Preston St.". There are well over 40 people listed as living "at side of Preston St." in Faversham in 1841. For over a year I'd thought it said "restaurant"...
Stephen Hughes is listed, aged 20, as a tobacconist, just below the family of William and Jane Swinyard, with whom he was living in a house in Preston Street by 1851. He was still in Preston Street (but in a different house) in 1861.
I shall contact you direct, as you kindly suggest.
Thanks again.