DVSA - do you know your signs? Mystery Cache

The Driving Test Centre for Dumbarton is located in Strathleven House. If you're about to take your practical driving test, this is where you will have to go. Good luck on your exam if it's the main reason for your visit here. 

A=1, Z=26
Ignore spaces where the wording contains more than one word. Pay attention to details. 

Giving orders

A = 7^th letter plus 19^th letter
B = 5^th letter
C = 5^th letter
D = 14^th letter minus 6^th letter      
E = 9^th letter
F = 2^nd letter

Final N55 58.ABC W004 34.DEF