I think this will be the main factor in how long these guys last as the weather forecast from 0C to 7C in the rain is perfect hypothermia weather. It will depend on the clothing that they intend on taking with them. If they go dressed in jeans and fleecy tops I would give them just 2-4 days in the cold and rain. Chances are they wouldn't be able to get a fire going and they seem to lack experience in building shelters. Simple open lean-to shelters or A frames probably wouldn't be suitable for the conditions they would expect to encounter. Some thing a little more substaintial would be required such the construction in the first few days of a log cabin or Teepee. A knife is not going to suffice in the constructing of one of these. A proper woodsman axe would make all the difference rather than a knife for medium to long term survival requirements.

Also the low temperatures and moist atmosphere will make fire lighting using friction methods a low probability of success. If they got the fire going they would have to ensure that it didn't go out. This effort will rob them of the time they think they will require to go hunting and fishing. The lack of cordage will make successful hunting and fishing again a low probability (they will probably end up attempting to use Bear Grylls method of throwing a big stick at their game).

Their inability to boil water efficiently by not taking a metal cup or pan will either make them ill or lead to dehydration although they could always improvise rain water collection method if a poncho was part of their everyday clothing.

So if they have the ability to build a substantial shelter in the first few days (depending on the weather breaks) and can get a fire going then they may last 10-14 days before they get to weak from hunger before abandoning their adventure.

If they took a good axe, a firesteel, paracord, a fishing kit and a large metal cup whilst clothed in good insulating and waterproof clothing then I don't see why 30 days would be out of the question. But they would still be suffering in their hole in the dark with an owl.