what disc brake pads do i need

[Grahame]

Basic differences:

Organic pads - mostly resin content. strong braking, good insulation of heat (ie don't transfer heat to the fluid and "boil" your brakes on long downhills), unfortunately, they wear out quickly in the wet.

Sintered pads - higher metallic content. slightly "weaker" braking, less insulating (ie transfer heat through to pistons and fluid more quickly, may "boil" your brakes on long downhills - think alpine or rocky mountain downhills rather than most UK), longer lasting.

In summary, for UK use I'd go with sintered. Shimano brakes use mineral oil rather than DOT type brake fluids, mineral oil has a higher boiling point, and you are unlikely to boil your brakes in the UK.

I use cable operated discs when I'm in the Rockies 'cos I'm a chicken and use the brakes a lot, and it would take a huge downhill to boil a steel cable, even with sintered brake pads.