Im not 100% as i see it a pointless way to go around things, but I think you need to provide the paperwork that goes with gundog training ... certificates of enrolment/merit etc. I say this is pointless (if it is the case) as by the time they have matured to do training, docking their tails if not done right can cause massif infection resulting in more and more tail being docked and a lot of distress. Vets if they are familiar with the breeder and their activities will dock - but I doubt your going to find one in central london if you know what i mean.

Springers are docked as they can break very easily and yes get torn in brambles. I know of springers tails breaking or becoming sore and inflamed even through wagging because they do it so hard on knocking it against things, I dont see it as barbaric in the least, though it definitely has to be done by a professional if at all.

Wouldnt really advise pulling any dog from a hole by its tail either