100% Maris Otter definitely won't hurt the beer - might make it better, might not notice a big difference.
Honestly, the real consideration in regard to 100% british pale ale malt, or 100% 2 Row or 50/50 is cost. 2 Row is just cheaper. Honestly, the interesting thing to do would be to brew one with 100% Maris or Golden Promise and the other with 100% 2 row and see if you can really tell the difference...... if not, 100% 2 row would be the way to go because it would save a fairly decent amount of $$$.