The Welwyn Roman bath-house is preserved under a special vault under the A1(M) in Hertfordshire. Details about visiting times can be found here (along with pdf guides in English, French and German). Tony Rook produced a small folded card guide (for 10p) on behalf of the Welwyn Archaeological Society (1975). A notice about the “Dicket Mead” excavation (as it was known in 1972), conducted by the Lockleys Archaeological Trust, appeared in the reprint of J.B. Ward Parkins, ‘The Roman villa at Lockleys, Welwyn’, The Antiquaries Journal 18, 4 (October, 1938) 339-76 (my copy has a pencil price of 50 p). The reprint contains a short introduction by Rook. Lockleys is close to the bath-house.