David, the NSbS was been published by HMG
here in 2016, although I agree that its not an easy read, it does make 34 clear recommendations, of which almost all have been 'accepted' by HMG (whatever that means in political circles), however although they were accepted - I think very few have been actioned, which is likely a contributory factor in the sad loss of 2 UK shipyards in the same week.
I think that the Global Combat Ship (Type 26/31e) programmes future export success is one of the positive signs that the NSbS strategy could help UK shipbuilders export both ships and designs overseas, however I think it may have come too late to save some of the Shipyards identified as suppliers in the programme (Appledore, H&W and Fergusons).
Either way we look at it - as you state, any competition in the EU is difficult and skewed, due to many of those competitors enjoying state subsidies (Navantia Spain, DCN France and yards in Italy) to keep the yards in operation when times are tough....certainly not a level playing field for struggling UK yards.
Perhaps partial nationalisation may be the only way to save what little is left of UK shipbuilding - before its gone forever as Bob stated earlier, but it would need to be a better model than the last time (for example yards were not allowed to compete with each other for work and the Naval yards were not allowed to diversify by building Merchant ships).