Some greys live very happily with smaller dogs, whilst others cannot stand smaller dogs and would not tolerate one. I think your best bet is to give Celia a call and have a chat. The contact number is on the homepage of the GRF site.
I agree with Steve to contact Celia and Jimmy. We have 1 greyhound and 2 lurchers all from Celia and Jimmy and we have a bedlington terrier as a next door neighbour. All 3 get on really well with her even though she is fairly small. But it all depends on the individual dog, which C & J can help advise you on, just definitely don't rule out a greyhound !