I know every little (is supposed to) helps, but I don't think having LED/energy bulbs all over the house helps much when you factor in their cost. It'll take several years for them to pay-back.
Not really.
Swap a 50w halogen bulb for a ~5w LED, saving 45w.
Assume 3hrs per day use= 135w/hr (0.135kw/hr) per day
0.135 x 365 = 49.3 kw/hr per year
@ 13p = £6.41
So it's more than paid for itself in 1 year.
You lose out on its heat output in winter, though. So may, in theory, use a little more heating.
Quite a few assumptions there. Unfortunately, none of them apply to my situation. It'll take me between 5 and 10 years to see payback. (Assuming the bulbs lasts that long. They have a 5 yr warranty.)