London lost 14-12 at Whitehaven last week in a game they could have easily snatched.
That performance came just a week after their shock win over Rochdale Hornets.
Mbu said: “The last two weeks haven’t been too bad. The boys have been working hard and they’ve shown they’re all up for it.
“They’ve been keen to get out there and prove themselves. We’ve been building up week by week.”
Demetriou said: “We should really have put them to the sword, but we came up with error after error, penalty after penalty, and then let in two of the softest tries we’ve let in all season.
“We’ve got to be more ruthless with our defence. We showed how good we are in patches, but the challenge is to show that for 80 minutes.”
He added: “Our discipline killed us. Every time we got down their end we’d let them off with a soft penalty.”