Considering you're in the UK and have a limited budget I would advice getting a dragon's tongue with slurrystone from inigojones.co.uk and a PHIG (chinese 12k) from theinvisibleedge.co.uk. It won't be a great setup but it will work albeit slow and will only cost about £27 + shipping.

Then your progress would be: diamant sharperner > DT + slurry > DT > PHIG.