They should give all they earn to be shared amongst their victims,
6 months for robbery @ £100 a week = 2.5K. OK not a fortune but something for the victims to share at.
Or heres a thought(tongue in cheek) !
lets put a ( artificially high) value on things of approx 4x actual value
plasma TV £2K
Jewelry 4x insurance value
window breakage 4x cost to fix
etc
then when they get sentenced its a simple add up what they "owe", divide by £100 = number of weeks inside

No early release untill its paid or they pay the 'fine'.

payback for the victims of 2x teh value and income for teh goverment, (think tax on being naughty!

)