You are taking a pessimistic view on the wind power side here.
In Denmark, we just completed a 400 MW offshore site which gets a non-inflation-adjusted strike price at 0.19 USD/kWh for the first 10-12 years. After that it operates on market terms. The capacity factor is expected to be around 45-55% as far as I know (other offshore sites have similar factors - the numbers are publicly available in an open catalogue of all Danish turbines). Modern turbines have much improved capacity factors compared to the old smaller ones.
Now in Denmark, 0.19 USD/kWh was considered a far too high price. The bidding round was hastened through so we only got one bidder. An earlier site received less than half of that in strike price. The latter one would be around £59 per MWh.
I don't know why you are paying so big subsidies in England, but it seems fishy.
While it is true that offshore turbines have a harsh environment, it's also true that the industry has learned from some of its early mistakes. Even if you don't believe that, you need to take into account that the foundation is the most expensive part of an offshore turbine, so even if you have to replace the generator and blades, it's going to be a lot cheaper than building a new farm.
PS: I don't think it really makes sense to quote EPR costs from China. The costs of things in China just aren't comparable to the costs in a Western country.