This doesn't help a lot, but in 1841 could Phillip be in Edgbaston in the household of James and Mary Rodway? He is aged 40 (James and Mary are 30 and 20) and both he and James Rodway show "M" as occupation -- merchant? James would presumably be a relation on Phillip's wife's side. The only other person in the household is a servant, i.e. no Susannah Mills wife of Phillip.
(Edgbaston is where Philip and Susanna Rodway married in 1823.)
Also just to note from the other thread (because I was looking around with the wrong date):
Julia Fanny Mills was christened
1832 1827 Birmingham
edit - James B and Marianne Rodway in 1851 and 1861 are in Edgbaston where he is a commercial traveller and then a brewer's maltster. Their children include eldest daughter Susanna (c1842) and daughter Annie Julia (c1852). But there are no Mills-s with them. He was James Barron Rodway who married Mariane Pensam 1841 Birmingham.
Have you seen the items in the London Gazette?
1823:
http://www.london-gazette.co.uk/issues/17892/pages/177Notice is hereby given that the Partnership lately subsisting between us the undersigned, Philip Henry Mills, John Rodway the younger, and Josiah Ashford, of Birmingham, in the County of Warwick, as Merchants, under the firm of Mills, Rodway, and Ashford, was this day dissolved by mutual consent ...
1828:
http://www.london-gazette.co.uk/issues/18469/pages/938- same thing re partnership between Philip Henry Mills and John Rodway the younger.
So he was in business with the Rodway family before he was in bed with one.