Maybe trying a few more tailored items to see what suits his body shape and flatters, rather than wearing something that just fits, which is what my DH used to do. Grey Fox is a good blog for men. Items are often expensive, but it is good for styling, colours and is not about following fashion. www.greyfoxblog.com/ Have a look at Landsend for basics, large department stores for brands not otherwise on his radar and just have fun trying stuff on.
Casually he wears a lot of (non team specific) rugby shirts with jeans which suit his build. Jacket wise a well cut blazer - he has a lovely dark blue tweed one for example - works really well. Ted Baker, style wise, often have nice looks although we tend to get a lot of his clothes in Debenhams as they are well cut for big shoulders!