@lettersbyowl - I have no idea why you would want a Westie crossed with anything, rather than just a Westie! Best dogs in the world
I'm afraid you're wrong there. They are almost the best in the world. I have a westie and a westie/crocker cross and while the westie is amazing [whisper] the cross is a nicer dog [stop whisper].
Mind you, she is very unusual in that she has none of the negative personality traits, other than a tendency towards stubbornness, of either breed. The only negative with her is that she sheds more hair than she actually possesses every day. My vet adores her and always comments on her amazing attitude and personality.
To the op - why are you looking for that particular cross? Is it simply that one is available or are there other reasons?
What I would suggest doing is looking up both breeds, assume you will get all the negative characteristics of both, and decide if a dog like that would work for you. If yes, then provided it is well bred, with parents who have had health checks, you are good to go. If not, then maybe look at individual breeds.
We originally went looking for a westie but heard of an accidental pairing (owner of male dog minding female dog belonging to his son when dog in heat). Both parents were very chilled and were well bred from a health perspective so we took a chance on her.