So I've had to communicate with my group by email. I emailed them on that first Monday to let them know what I was going to do, then sent another on Wednesday with the results I'd come up with. I didn't hear back until Friday - almost a week with no contact, and no idea what they were doing. Then I had an email the following Tuesday, then finally a flurry on the Thursday just gone.
What is extremely worrying is that they seem to have no real clue as to what they're doing, but the assignment is the sort of thing I do for a living. They only seriously asked my advice on Thursday, five days before deadline date. I tried to provide it, but being so far away it wasn't immediately obvious what they were doing. This morning it dawned on me that they have taken completely the wrong approach, and it's now too late to change things.