Does anyone have any real views (ie, not theoretical ideas where we don't even yet know how to approach them) on services which a bitcoin business could offer with some investment? If it is of any help I am UK based too.
Well are you looking to invest or to donate?
If it's the former, you might consider a seat on MPEx. S.NSA for instance is currently working on a usb stick-style device to allow GPG signing and decrypting with actually complete security.
If you were leaning towards donation, there's the Bitcoin 100, or Phinn's feed the homeless thingie.
I'm not aware of anything worthwhile that develops bitcoin tech on a pure donation basis, it's pretty much one or the other.