The cache is not at the published coordinates, which are a good place to park. There is a wide variety of food and drink available at the adjacent Beaconsfield Services.
I start with an apology to Uncle E for using the same title as his cache, GC34N0H, a part of his excellent Alphabet series, although the themes are wholly unrelated.
To discover the coordinates you must first identify the following sequence that is both familiar to millions and familiar with millions.
H C R B D V
The cache can be found at N51 (R + (D * H)) . (B + D)*(C + R + V) W000 (2B + 2V + D) . ((((B + H + V) * R) - 3) * D)
Access to the cache is along a good footpath but the final 20 metres require sensible footwear. It is useful to possess a walking pole when it is wet. The container is a click-lock box, 90 x 90 x 50 mm, containing only a log sheet. Please bring your own pen. When replacing the container please cover it well.
Help is always available. I want you to find my cache. Congratulations to Lindylew, mserafim and Uncle E, all of whom solved the puzzle before a hint was added.