I know the difficulty you are having as I used to wear larger sizes (22/24) myself and now have a couple of boxes of clothes that are too large for the new slimmer June.
If buying on the high street Evans was my main supplier until Bon Marche came on the scene.
Once you work out your size try Bon Marche – they have a reasonable range of clothes and are quite happy selling to men.
I even have a Bob Marche loyalty card in my wallet/purse.
Hope this is of some help to you.
Don’t forget the shops/catalogues need to sell their stock so do not really care who they are selling it to.