London North-western suspended the Bedford - Bletchley service was last week replacing it with a buss until further notice, LNR says due to Vivrail going into administration this therefore means that there is no guarantee of maintenance for the trains on the route.
Looking at Real Time Trains there are buses shown, intermittently though, into January. Where it's a train, it takes 41 minutes end to end. Where it's a bus, 83 minutes.