Aw hun, sorry to hear Mango's diagnosis, if you can post up the creatinine and urea readings then we can compare them to our respective babes readings etc
Max was insured with AXA, and we always managed to get bills paid even with the FIV, my vets were adamant the 2 were not related as such, and pushed through each and every claim, which covered the drugs, as well as the ongoing blood testing etc, so you should be fine with them, they are a good company
At this stage don't worry, things will become more apparent over the coming months with the repeat blood tests, then you can monitor whether this is some kind of acute renal issue, or actual CRF which can be treated successfully.
I'm sure you vets will give you lots of advice, but there's loads of us on here who can help as well, so just ask with any questions you have. I can remember only too well feeling scared at the diagnosis, but there's no need to be, even if CRF is the official diagnosis, if caught early enough and with the right treatment, cats can go on to live for a few years beyond diagnosis. We lost Max a year and a half after he was diagnosed, but he also had thyroid problems, and was older, so was more difficult for us