
I personally would want a second opinion, and quickly, the postal strike shouldn't really affect them getting the results as emails and telephones can be used for this. You need to be sure they are treating your boy with the correct antibiotics, if these are not working then they may not be the correct ones for this particular infection and some infections spread rapidly.
Just out of interest, has he recently had a booster?
Insist on a referral from your vet and I'd do it today!
Let us know how you get on.