100 quid? – i'd get 2 fenix L2D's.
1 with the 'spot' reflector, 1 with the 'flood' reflector.
that would give you about 200 lumens for about 4 hours*.
i like to have the brightest light on my handlebars, so that any bumpy trail features will cast long shadows that i can see easily.
if the light on your head is too powerfull, these shadows get filled in – you can't see them, so trail features get harder to see.
imho etc.
(or about 400 lumens for 2 hours, or about 100 for 8 hours, or mental combination of lights and flashes and strobing and light intensities and run-times)