All latitudes in the UK are 50-something or other (except for the islands to the very far north of Scotland which are 60's).
Therefore, simply take the first digit of the Dange Area code and that will tell you what latitude it lies to the north of.
D117 - North of 51 degrees North
D307 - North of 53 degrees North
You will note that some cross the line of latitude, e.g. D203 (mid Wales) originates north of 51 degrees North but the majority lies to the north of 52 degrees North, hence the '2' designator. Similarly, D308 lies in the majority to the north of 53 degrees North with a portion to the south of the latitude.
The next two digits are simply numerical idenitifiers and have no geographical relevance.
D703/15 lies to the north of 57 degrees north, is Danger Area No.03 and extends to 15,000' AMSL.
HTH
2close
Edit to Add: Sorry, Patrick, we crossed over!