Quite right, DMcG. And let me quote a relevant section of those guidelines for negotiation:

II. A phased approach to negotiations

4. On the date of withdrawal, the Treaties will cease to apply to the United Kingdom, to those of its overseas countries and territories currently associated to the Union, and to territories for whose external relations the United Kingdom is responsible. The main purpose of the negotiations will be to ensure the United Kingdom's orderly withdrawal so as to reduce uncertainty and, to the extent possible, minimise disruption caused by this abrupt change.

To that effect, the first phase of negotiations will aim to:

provide as much clarity and legal certainty as possible to citizens, businesses, stakeholders and international partners on the immediate effects of the United Kingdom's withdrawal from the Union;
settle the disentanglement of the United Kingdom from the Union and from all the rights and obligations the United Kingdom derives from commitments undertaken as Member State.
The European Council will monitor progress closely and determine when sufficient progress has been achieved to allow negotiations to proceed to the next phase.

There has been no breach.