When you enter on an O-A they will only stamp you in for as long as your health insurance is valid for (up to 1 year from entry). Most are one year policies I believe. If you know it will only be a few months before you'll be covered by your wife's insurance then you could go with Tune insurance which does monthly, however I think thats closer to $100 a month and you'll also have the expense of departing a d re-entering with the new policy so may not work out at any cost saving. If you're going to be covered from your wife's then just go for that hefty excess policy and think of it more as a fee for not having to tie up
shouldn't be too much higher then. Check out misterprakan.com brokers for your O-A insurance options. Somebody mentioned the other day that you may be able to use a policy for from your home country that would be suitable but the ones on the above site are guaranteed to be acceptable
What kind of age are you Bill? If early 50s you can get one years health insurance for the o-a visa for about $500 (with quite a hefty excess if you actually want to use it) but the older your are the heftier the premium is
If you're still resident in UK then even with Polish passport you can apply for an e-visa. If you're back in Poland then it will be the old fashioned way