Ia BIG gamble. I don't ever want to be in a situation when i cannot afford to give my piggy the best care possible because I cannot afford it. It also adds to the stress when you least need it.
I had one piggy cost me in a period of 3 months £1,500 to put right. She was not insured but I was fortunate I had the money but I wish I had had her insured. After that I insured all the others.
Since then I have now insured 5 out of the 6 I have (the other one is too old) and so far whilst I pay £40 a month for 5, I have been better off for the last few years! But equally I probably ask the vet to do more than I would if I did not have it.
I have been unfortunate, one is a heart pig and needed xrays etc, another had to have two lumps removed on two separate occasions (with biopsys etc) and then another is a dental pig, I also had two 'bladder' pigs which required ops.
With the dental you are right, if damage is caused whilst having a tooth trimmed then they will not pay up. In my case they did not pay all the bill but they have paid for a lot of the consultation and ongoing antibiotics and complications.
So for peace of mind, I would not do without it now...I know I can give my piggies the very best in care, diagnostics, xrays etc, etc and not worry too much about it. But i can see how £40 is a lot of money per month but with five piggies it can be very easy to spend £480 on vet fees in a year if you have a run of bad luck. Its just personal choice I guess.
I use Exotic Direct who have been very helpful and pay up very quickly.
https://www.exoticdirect.co.uk/