@adrianwray
If your lawyer is helping you with your D visa application, then my guess he's simply referring to the private insurance most folks buy as part of their application. This is the Medical Insurance for Foreigners in Bulgaria. This is a policy to keep immigration happy, and it's merely an emergency/repatriation insurance. It pays out, but only in very narrow circumstances... and it's a completely different animal from either the public health system (NHIF) or proper private medical insurance. It would be completely unwarranted to draw negative conclusions about Bulgaria's health system (or its private healthcare insurances) based on a throwaway comment on a worthless immigration policy. It usually costs less than 100 euros, nobody expects it to do much for that price). :-)
I've been here for nearly 8 years and I'm a Bulgarian PR. We all have different experiences, but I've certainly found a great life here. There are many positive aspects to life in Bulgaria, and it's one of the best decisions I've made. It's been such a positive one that I moved my father over last year, and I'm caring for him here (he's 97, and has his S1). Even if your healthcare experiences were nowhere near as good as mine, there's no way it's sufficiently bad to be a deal-breaker! :-) Personally, I find it works very well.
You can access the public system by making monthly contributions (as employed, self-employed, or unemployed) or by having an S1 from the UK/other EU country. I pay 20 euros per month, as unemployed, for full public coverage. (My dad's has his S1, so he pays no regular contribution at all.) Public hospitals will provide you with free, or nearly-free, treatment/operations. Like the UK, it works via your GP who refers you to the appropriate specialist or orders the necessary scans/tests.
Most of the private hospitals are affiliated with NHIF, and also reimbursed by it. But, naturally, they're more expensive and there's a private surcharge. If they're not affiliated with NHIF, or you don't have public coverage, then you pay full price.
You can pay for private treatment out-of-pocket, or you can have a (proper) health insurance that covers it. There are several very reputable companies and I'm very confident that they pay out. Like everywhere, these policies get more expensive based on age and prior medical history, and often have deductibles/exclusions. As you'll have your S1 (and public coverage) then an unfortunate exclusion would not be a huge drama for you. My guess is that a policy would be less than 1,000 euros, but you can check with a couple of providers/brokers.
If someone is covered in the public system (as I am because of my contributions), then a private policy is substantially less expensive, because the public system will cover most of the cost.
I'm actually still a legal resident of both Spain and Cyprus, and they are both delightful countries with beautiful Mediterranean beaches. And they're deservedly popular with tourists and expats, and especially retirees. If I were a wealthier man, I would be living in a beachfront villa in one of those two countries! I can't claim that Bulgaria is in the same class, and the Black Sea is very much the Med's poorer, dirtier cousin. :-) However, I appreciate Bulgaria's charms and positives... and find it compares extremely well when you start to factor in the cost of living and cost of property. The reality is that we live FAR better here than we do/could in either Cyprus or Spain, and hence I spend most of my time here.
The public healthcare in Spain is very good, but the Cyprus system is relatively recent and I don't know how good it is. BUT the public/private cooperation discussed above is not present in either country. They, just like the UK, give you the choice between free, slow (but good), public treatment... or full-price VIP private treatment whenever you want it. Whereas, in Bulgaria, I can get the latter at a ludicrously small private surcharge because of my 240 euros a year NHIF contributions (or my father's S1).
Medical stuff is not enjoyable per se, but I find that I really enjoy this luxury option. And, indeed, I compare it with the alternative of standing in line for public treatment in Cyprus or Spain, and conclude that I don't want to be sick... but if I am, I'd rather be sick here. :-)