Death Line is a sub-Hammer British horror film from the early 70's and it's only redeeming feature is an amusing turn by Donald Pleasance as the snarky detective tasked with unravelling the mysterious disappearances from Russell Square tube station. I guess the shortcomings in plot and acting were supposed to be counteracted by plenty of gore and the gruesome fx but these have dated badly leaving little to recommend it. If you want a underground based horror I'd go for Creep instead - a remake in all but name.
Dark Mirror was a little better but it squandered it's semi-interesting take on the Haunted House trope by some shonky acting and a meandering second half. It's pretty low budget so they decided to try for a creepy atmosphere as opposed to general horror scares but they never quite manage it and it ends up a little dull.
Mutants is the first french zombie movie ever I think and though it's basically a 28 Days Later ripoff it wasn't terrible, phew. There's no preamble explaining what caused the outbreak which was nice and just starts with a small gang of survivors dodging the plague ridden people-munchers while searching the Alps for a military base and some sanctuary. It's festooned with cliches and gaping plot holes but the acting was reasonable and it's well shot and it even managed a little tension without just turning into a human buffet. Maybe it's coz of the two duds above but I quite enjoyed it and will probably watch a sequel.