I reviewed the devolution for Scotland during the first Independence referendum (there might be a 2nd, soon)-http://dougsarchaeology.wordpress.com/2014/09/15/what-an-independent-scotland-would-mean-for-archaeology-and-heritage/
But, the results are about the same- Scotland, England, Wales, NI, even Isle of Man have very separate systems already. Funding is separate, organisations are separate, laws are different, etc. etc. There is CBA in England and Wales but Archaeology Scotland in Scotland.
There might be some difference for Wales and England that are under the same laws and that might split up. It COULD (but, could not) help with central government funding. Right now English Heritage- soon to be Historic England is under the same budget as culture, media and sport. Technically the same budget that paid for the olympics. A developed England might mean that funds are not taken from EH (not actually taken but over the last decade the UK government has not increased the budget of EH above inflation which has resulted in massive losses). Or it could all go sideways and England decides to scrap archaeology laws, funding, etc.
At the moment because of the devolution that does exist in the rest of the UK a devolution of England will probably have very little short term affect. In the future it might matter but I would be willing to bet not much will change.