I think Richard and TLR are definitely going to end up dead.
The worst ending for Catherine would be Claire dying, especially as they remain unreconciled.
I wonder if Alison has been reintroduced only so she can be murdered. If TLR heads for Catherine's house she is the person most likely to be there at the moment. If she is bending over that car, she could be mistaken for Claire from the back. Maybe that's why she mentioned doing her own highlights?
It would be hilarious and fantastic if TLR rocked up at Catherine's house only to have the world's worst misfortune in encountering the one woman in Yorkshire who has already killed a serial killer. Right when she's holding a big wrench too. She could thwack him and get on with that alternator and then they'd have 1hr and 50mins on the woes of the PE teacher, and Joyce wandering around Hebden Bridge trying to find a £2000 leaving gift for an absolute ballbreaker.