This morning my dog has been wheezing like mad!

what can this be?

BTW she hasn't been in kennels for about 2 years.

It could be many things - best to take her to the vet to find out exactly what is wrong

It has stopped now though. Should I still bother?

That's a difficult one - and only you can be the judge. 

Have you had a listen to your dog's chest to see if there is a wheeze to be heard there (only if you know what normal breathing sounds like), is he acting normally or running a temp?

I would probably try to make an appointment for first thing tomorrow morning in case fluid is collecting overnight and causing a problem when he gets up but warn them that you will cancel it (as soon as they open) if he is still breathing normally.

There are many causes of wheezing apart from kennel cough which I assume you were referring to (and they can pick that up anywhere).  Heart problems, asthma (yes dogs can get this) chest problems etc.  If you are at all concerned then I would see the vet just to be on the safe side.

I only went to the vets yesterday about her itchy ears which she has had for years. They said this could be ezcema or an allergy.

Could this be related?

I cannot afford to keep going back to the vets, but if I have to I will or I will take her when I get her booster done.