SideTracked - Poole #2 Mystery Cache

This is a mystery cache.

Please do not search for the geocache at the dummy co-ordinates which are the High Street footbridge across the Weymouth, Dorset to London Waterloo railway line, which actually crosses Poole High Street at this point.

If you arrive at the right time, the barriers will close and you can witness the train traversing the High Street, quite a novelty!

The geocache co-ordinates are N50 43. ABC and W001 58.DEF

Where

A is Dorset 2nd minus 5
B is Dorset 8th
C is Dorset 4th minus 12
And
D is London 6th minus 3
E is London 4th plus 3
F is London 2nd plus 7