Lol like Shabba has said, you have to use all your points allowance for the week, and then with the AP, say you earned 16 AP points throughout the whole week, along with your weekly allowance your only allowed to use 12 AP point that you have saved food/drink wise.
therefore if you have saved say 4 points throughout the whole week from your normal weekly allowace and then earned AP also on top, the max you can go to with AP is 12, therefore meaning 16 points spare that you need to eat.
HOWEVER! you will have to do an awful lot of walking to earn 12 AP tbh! it's really ridiculous the amount of steps you need to take just to earn 1 point, something like 10,000 so you basically need to be walking at a high intensity for a few hours to get 12 AP
if you really want to spend 16 points on booze (for the sake of this i'll use 15 points as it's easier) if you drinking beer, that's 5 pints. or 10 halves

in spirits your looking between 0.5/1 point per single measure, so that's 15 singles, or 7 doubles and 1 single lol as long as you have diet mixtures to go with drink , best way to ensure you stay within points also, is to save more weekly allowance points to cover drinks rather than rely on the walking to earn you 12 AP for them

as if you dont actually earn 12 AP and then you havent saved enough you will be going over for the whole week lol

for a good walk i'd say between 4-7, depends on the intensity (low, med, high) best to ask Pugso as i know he does a lot of walking also

good luck and enjoy London x