Note that Bachmann (UK) has announced a ready to run 009 range although these are yet to appear. Other companies have also announced some ready to run items, some rolling stock is currently available. Of course the Thomas narrow gauge items can be converted to represent their prototypes. In terms of mixing 009 and HOe purists don't because of the scale diffence but many do, noting that narrow gauge equipment varied in side a lot anyway. It's up to you.
Hamish
Hamish