I've used MapRun quite a lot on the Three network successfully. What do you mean by 'data only'? Do you mean via 3G/4G rather than wifi? If so yes - it works fine for me.
Thanks Simon, yes I meant via 3G/4G, I'm finding it is very hit and miss (as is my son), I do think it is a problem with the three network, we just make sure we've chosen the event via wifi before we go out.
Three are not the best for rural coverage and their speeds can be hit and miss. Same i guess with all networks, but three I've found are more patchy than most.