One or more dns entries pingable.aa.net.uk

or similar meaningful name as a first-hop within AA-land target for pinging, perhaps a cname to bottomless. Anyway, way you can change its target when you need to. As well, two additional cnames, ipv4.pingable and ipv6.pingable, say, to the same target would be nice so you can more easily select which protocol to use. If possible some other ping targets with meaningful names, within AA-land.

And if the following is even possible, then additional ping targets closer to the user than AA - prob not because of tunnelling. User would need to be clued-up enough to only pick the correct one according to their wholesale carrier, unless some serious cleverness is possible, which would be brilliant.