Yep, you can have a board on the nipper. I had a kiddyboard(the version which clips to the back axle) on mine.
The weight(or lack of!) was the main reason I chose the nipper - have lots of steps to bump up to the school playground! So sturdy as well, and compact. I do have a newborn inner but have never used it(dd2 was 8m) - looks great for tinies though.
Have just looked at the Which? best buy table and it has changed somewhat from the last time I looked as most of the Best Buys seem to be Isofix. Will just post stage 0+ seats as presume that is what you are interested in
Maxi Cosi Cabriofix with Easyfis base
Britax BABY SAFE Plus(Isofix)
Mothercare Meteor with base
Recaro Young Profi Plus with base
Britax BABY-SAFE Sleeper
Jane Strata
Mamas and Papas Primo Viaggio Isofix
Mothercare Meteor
Mamas and Papas Pro Sleep IP(Isofix)
Britax BABY-SAFE(belted)
Chicco Auto-fix Plus
Hauck Zero Plus
There weren't any 0+ in the Don't Buy table.
If you want a more indepth review of any of the car seats I can probably cut and paste. HTH