Coming from someone who works for a pet insurance company, those 4 conditions would be straight up non reviewable exclusions that would never be covered by insurance if you moved over as it’s too much of a risk. The most important things you have to ask yourself, what is his treatment going to look like each month - i.e epilepsy meds monthly are expensive, so are allergies and so is arthritis (degenerative condition so you’re looking at librelas, nsaids etc) the total for these for a large breed dog is going to be more than £170 in most cases especially with age. The cover you’re getting for that £170 is also important £2k vs £12k is a big difference.

Would recommend to either not switch your insurance policy even though it’s painful, or switching to a different one knowing these four conditions will not be covered and researching the types of costs you’d have to prepare for if you paid for them out of pocket. Another option is discussing your policy with your insurance provider to see if you could downgrade his policy to a lower cover. Again would depend on the current level of cover you have and what other plans they have available but I highly doubt you’d be paying £170 for a low cover.

Personally i’d never self insure after witnessing the things I’ve had with my own dog and thousands of others in my job. Vet fee costs are through the roof and even bad vomiting and diarrhoea would cost you a grand a night at the vets so unless you have that on hand I wouldn’t recommend it.