Garmin 800 enduro with OS maps or the Garmin road maps inc European maps?

Hi
I am deciding between buying the Garmin 800 with OS maps and the Garmin 800 with road maps (inc European maps). I originally thought I would buy the one with the OS maps. What are people's experiences?
I would use it for:
- long road cycle rides in the UK (main use)
- commuting in London (also main use)
- walking/hiking (less so but would be useful and really great to have the maps).

For example, if I am commuting in London will having the OS maps on the enduro version be a problem?
Will I not be able to see clearly which roads to take and will the detail of small urban roads be less on this version?
Can it also be used for running?

thanks
Satu