I have a five year old Dalmation who is in season at the moment (9 days in) and I do not know whether to mate her or not as some people say that because she has phantom pregencies I should let her have a litter and then have her spade.  What are your views ?

I think you'll find that at 5 she is way too old to consider letting her have a litter safely.  If the phantoms are affecting her health, then why not just get her spayed?

IMO 5 is to old to have a first litter and you would have needed to start looking for a suitable stud months ago. If you and your vet are unable to control her phantoms it would be kinder to spay her, no need at all for her to have a litter first.

Have her spayed. She should not be having her first litter at 5. It is nonsense to say she should have litter because she's had phantom pregnancies.