I'm thinking your concerns should be more long-term than short-term. For example: The current approximate population of England is 53 million, living on 50,301 sq miles (32,192,640 acres), which is equivalent of approx. .6 acres per person. If my math is correct, only approximately 53000 people remain (607 acres per person).
Let's say (worst case), your group came out of London- current pop. 8.788 million (who could expect to have had 8788 total survivors -- not counting any who died after the initial plague?). With the total square miles of London being 611 (391,040 acres), each survivor would have had app. 44.5 acres available... of city scape - crammed with businesses, homes, all sorts of stuff everywhere! If the stores were stocked for 3 days' supply (as is typical in the US), let's assume the food stock on hand when the crisis began was 8,788,000 (# people) x 3 days = 263,640,000 person day's food supplies. Let say that 2/3 was perishable -- that still leaves 87,880,000 person-day's of food. So... everyone didn't die on the first day, so maybe only half of that was remaining on the store shelves or in transport trucks at the end... 43,940,000 person-day's supply of food. If you divide that by the remaining 8788 people who survived the initial crisis, that still leaves approximately 5000 days' supplies of food available to each person -- not counting any fresh veges/fruit/fresh meat from hunting...
The abundance of goods, natural resources, etc. is huge, considering the very small percentage of survivors. While I agree about the need for gardening, cultivating and maintaining infrastructure, it seems to be that the threat of other humans is pretty small.
Planning for the future and especially for the survival of the race seems more important... and I don't think we need to worry about running out of food if more people join our group. we should welcome them if they can get along...