First rectification (UK) v. modification (EU). The EU is only modifying its tariff quotas. Its normal tariffs are unchanged, hence GATT Art.28, which requires negotiation.
The UK is copying and pasting the EU's normal tariffs => rectification works
So the UK cannot get away with rectification for tariff quotas
P.S. This does not deal with domestic farm support, which is also in WTO goods schedules
And a section on oilseeds. Yes, I know it was the breakthrough that helped conclude the Uruguay Round negotiations, but I hope I never have to read it