Night of the Living Room - Winter Geolympix 2018 Letterbox Hybrid

Set for the 2018 Winter Geolympix with permission from the National Trust. If you intend to attempt the Letter/Box Challenge on Mega day you may want to leave this until then.

A tall tale of four Undead fiends who shared a house...holder. Let's call them Zom-A, Zom-B, Zom-C and Zom-D. None is in the same room as another (Zombies are not sociable) and they're each eating a body part of Malcolm, who previously owned the house. One is not nice, one is ok, one is tasty and the fourth is delicious.

1. Of Spleen and Intestines, one is delicious and the other is being eaten by Zom-B.
2. Malcolm's Arm is not being consumed in the Bedroom.
3. The Arm is slightly less enjoyable than Malcolm's Spleen.
4. The body part Zom-A is eating is tastier than what is being eaten in the Conservatory.
5. The Conservatory contains Malcolm's brain or Zom-B but not both.
6. The body part Zom-D is eating is tastier than what's being eaten in the Lounge.
7. The body part Zom-B is eating is significantly tastier than what's being eaten in the Lounge, but not wildly better.

Here's a grid to fill in. Doing so correctly will help reveal the final co-ords.

Using the time-honoured conversion (A=1, B=2, C=3.. J=0.. Z=6) and dropping the lead digit from any two-digit results (eg if A+B=17, then call it 7) the cache can be found at:
N51 48.(A+B) (B+C) (C+D)
W000 35.(D+E) (E+F) (F+G)
where:

A = The code letter of the zombie who was in the kitchen.
B = The first letter of the item being eaten by Zom-C.
C = The first letter of the room containing the arm MINUS 1.
D = The first letter of the least tasty body part MINUS 1.
E = The first letter of the tastiest body part PLUS the first letter of the room containing Zom-C.
F = The fourth letter of the room containing Zom-A.
G = The third letter of the room containing Malcolm's brain.

Please DO NOT remove the stamp or ink pad. Neither is a swap - They make this cache a LetterBox/Hybrid. Thank you!

Cache inspired by several similar ones, including HHH20's Big G: Zebra, which is also at Ashridge.