Having searched fairly thoroughly to solve this problem I came across this answer which solves the problem for URL: Changing predefined words in a biblatex bibliography
Is it possible to perform the same task on the DOI label to give the result shown below:

DOIwith what? – Bernard Dec 05 '15 at 23:48Available from:immediately before theDOI. another option would be to change the whole sequence toAvailable from: doi:– Hugh Williams Dec 06 '15 at 00:15