Losos is correct in my experience vets don't normally test for all possible causes of a problem at once just a couple of specific things and then they work by a process of elimination testing for one thing at a time .
Some of the blood tests are very expensive, one I had done on Millie cost £78 so maybe that is why they don't test for every possible thing at once.

Not read all the threads, but please please see a vet. Loki had these symptoms and was diagnosed with kidney failure a couple of weeks ago. Excessive drinking and temperament changes are cause for concern!

Frosty has become frightened of things that didnt bother him before. He's ok with me but my husband he no longer trusts and wont leave the house with him. This week it seems to be the dark and in particular the garden. Hes taken to hiding away in strange places -under the bed and in the wardrobe (theres nothing to fear in narnia) he has done this before but usually only on bonfire night. When you try to get him out he will snarl which is totally out of character. What i dont understand is how he can last up 6 hours during in the day but only 2-3 in the night with out weeing. Last night he was let out at midnight then at 2am and when i got up at 6.30 we still had a puddle (a very large one too).

Loki started hiding too. He went in his kennel in the garden and wouldn't come out. He has never even used his kennel before, only our cats use it! I think that's just the feeling rotten thing. As for night wees, it's weird that when anyone (humans included, especially kids) is ill, it's always worse at night.

Thought you maybe interested in the latest.
Ive been giving frosty some seren-um in the evening and its worked! hes calmed down and is not having accidents anymore. I think it may have been in his head. Fingers crossed this will be an end to it. He is due more blood tests next week. We had a real fire put in over Christmas and im begining to think it all stems from there he hates change.