That's a kyphotic curve, nothing to do with his form
You're lacking flexibility though chappie, depth from the legs is poor. I'd say you've got tight glutes, hams and calfs, work on your flexibility, this'll also help address your (slight) postural dysfunction.
Otherwise, FF is your man
Ant
No YOU'RE tha man!
Looking back over the vid, I agree, it's clear that he's trying to do it right but lacks flexibility.
Tom - can you (without weights) stand and go down to a deep squat position comfortably? i.e. without falling over or losing your balance? Squat as low as you can with your bum nearly touching the ground (like you see kids do when they're "sat" playing with their toys or whatever). From there can you stand back up without momentum, pushing with your arms etc?
Maybe a bit of a warm up might help improve your flexibility for the exercises themselves?
Something along the lines of:
30s of jumping jacks
30s of mountain climbers (get down to a pressup position and basically run on
the spot bringing your knees up to your chest)
5 sets of fire hydrants with 2 sec hold at top for each leg
Rotating fire hydrants (5 one way, 5 the other way) for each leg
Glute bridge (12 reps with a 2s hold)
Prisoner squats (20 reps, hands clasped behing your head)
That should loosen up your hips and legs a bit. Do 6 reps holding each one for around 5 seconds or so.
Then after the exercises when you get home after a hot shower, do some calf, ham and glute stretches, adductor and abductor stretches, and hip flexor stretches.
It won't happen over night but it will gradually "open up" your hips and improve flexibility.