Congratulations on your new puppy! What kind of dog do you have?
I work in a veterinary practice so deal with pet insurance a lot. My advice is:
Go for lifetime cover. Not maximum benefit or 12 month cover as once it’s gone it’s gone. This is fine for things like a cut pad but for something like diabetes, heart problems, etc then you will be paying out once the policy cover ends.
Check there is no financial caps. One of the policies mentioned above is notorious for putting financial caps (limits) on MRIs/CT scans along with a few other companies.
Go for the highest cover you can afford. I work in a referral practice so a lot of our surgery/investigations are expensive so I would say to go for a minimum of £7500 per year as even in a first opinion practice it can still mount up.
Also consider if your excess has an additional 10% (this usually happens with older animals but some insurance adds it onto young animals too). A 10% excess is alright if your bill is a few hundred but if your vet bill in in the thousands you will have quite a bit to add on to your fixed excess.
Personally I use Pet Plan and have never had an issue with them, although they are a bit pricier than others. The cheap ones tend to be cheaper for a reason ie they cover very little. It’s not until you need to make a claim that you discover this as no one reads the T&Cs and they never divulge this when you take your cover out.
Hope some of this helps 😀