100km Races

I'd like to have a go at a couple of 100km races next year, to try and stretch out my 50mile pace/effort.  Nothing predominantly on road though, or that requires too much navigation.  I deally a 'quick' off-road/trail/track route.

Does anyone know of any, have any recommendations?

Thanks

London2Brighton?  It's the second May bank holiday weekend.

There is the UTSW race, Daz. They do a 100m and 100k race. Run by Endurancelife so will be a marked course on the South West Coastal path.

Thanks, yes that's the only one that came up for me so far.

Adventure Hub do a few 100km races, their Norfolk Coastal Ultra is next week...

http://www.adventurehub.com/Ultra_Races.html

Looking for something with a little pace though - light trails.  The Coastal races wont be quick lol