The stated co ordinates are not for the cache site.
You need to visit 2 signs which are close to the cache site for
the missing numbers that will lead you to the cache site.
Go to N51.19.893 W000.28.569 Fill in the missing numbers 01483
A55B55
Next go to N51.19.983 W000.28.716 Fill in the missing numbers
17C4D6
The cache can be found at N5C.C9.9A0 W000.DB.9BB