The bus on which Kirkwood and Watling first meet shows "Chalkwell Park" as one of its stopping points, which suggests that the location shots were done in Southend/Westcliff on Sea.
The book that Mr Lamb reads in the hotel nightclub is 'They Don't Dance Much' by James Ross.
The first time Irene is seen, the distinctive tower of The Kursaal is visible in background, placing the location in Southend.