Depends upon how old you are SimonCC - my eye's aren't as good as they were.
I managed a 20 mile each way commute, with 60% of that unlit, with my old BLT's - they cost me about £80 in the early 90's (those and Nightsun were the brightest). I used the BLT with a 3w front (adjustable beam in spot mode) and a halogen Ever Ready D cell unit for wide spread- was fine - they are still going strong.
They've had two replacement lead acid batteries over the years, and one additional halogen bulb. The batteries are only about £7 from
Maplin for a 4.8ah battery.
The current LED's are good - e.g. the 1w ones - I thought my older cateye (3 x led opitcube) was fine for the roads, but some of these new ones are fantastic.
You do need at least two sets of ligts, and maybe some 'backupz' attached to rucksack/pannier - dead cheap to run.
This is what my BLT's look like for those interested.......