hi does anyone know of a company that will deliver gusto?

Try Tesco online.

Its worth approaching your local independent pet Shops, many do delivery but dont advertise it.
  Your moneys better going to the small business that struggle these days in towns and villages against the big bully boy Supermarkets ;)
  Lost count of how many great long standing family run Butchers and bakers our area has lost to them! :rolleyes:
Ooop! I'll get off my soapbox now! ;)

If you can find another stockist, great - but Tesco is the only place I've seen it on sale! ;)