Your folate is high. This happens when B12 is low. Another more predictive blood test is MMA.Your B12 is very borderline and dropping. The reference range for B12 is outdated from your lab. Oral tablets here do not require a doctor's RX. You can take them yourself. There is a B12 sticky at the top of this page with information about that.

Did you have a Vitamin D test? I don't recall if you stated you did.

There are people who cannot methylate properly. This is a genetic failure and requires active forms of Folic acid called methylfolate and active B12 which is methylcobalamin.
There is a test for this ...the MTHFR test. There are about 25 genetic polymorphisms that result in failure of these two vitamins. A high folate reading either means it is building up in your system (not being used) or you are taking it orally. Since you are on Pentasa which depletes this vitamin, and you tested high for it....are you taking it supplementally?

Many doctors do not consider viral titres...it is because they didn't have that in school. Your onset is pretty sudden, and suggests an activation. You can have pain without lesions.
If you suspect this you can start on l-lysine. This does not need a doctor's order. I don't know the laws in NZ on supplements tho. On importation etc. See if you can find it.
iherb.com does ship to NZ.
http://www.iherb.com/info/shipping/International

If you Google "shingles pain without rash" you'll find many hits.

My husband and I have both had shingles (herpes zoster) at different times and in different areas. Mine were down my right arm. I have had pain from my neck (stiff neck) there down the arm at least 4 times with no rash. Mine was in response to working midnights--and the resulting stress. The vesicles on the first attack were minimal too. My husband had his typically around his trunk, and had pain once after they healed...about 1.5 yrs later in his back where the rash was. His was within a week of a severe bee sting which seemed to trigger it. He also had the shingles in his ear. (this was very unpleasant)

I had the titres drawn by my doctor and the result was very low herpes simplex and very high off the charts herpes zoster. This test was done just after the eruption of the vesicles.

You might have to consult an infectious disease specialist...who can also test you for Epstein Barr virus, which is also thought to activate. There is another virus called HHV6 they can test for too.

If you don't intend to get the B12 MMA test, you can start that now, and see what happens. If you intend to get the MMA test, don't start the B12 supplement until after it, to get an accurate reading. Some places in US only use this test now to screen for low B12 problems. Mostly in the elderly where it can be a hidden problem.

You can also start the L-lysine, as this should not interfere with B12 testing. If you start to get a response of any kind (don't expect a cure), this will point you in the direction of viral serum testing.