Chris you are right I can not see anywere mention of the S1.
The Independent 3 days ago wrote
" It is understood that the European Commission is at this stage only prepared to agree that UK citizens living in the EU at the time of separation should keep access to their EHIC." and " Brexit Secretary David Davis said the retention of the EHIC for people already living in other member states was “good news for example, for British pensioners in the EU”.
“It means that they will continue to have their health care arrangements protected both where they live and – when they travel to another Member State – to be able to use an EHIC card,” he said"
It says travel to but not actualy say that the actual visit will be covered. http://www.independent.co.uk/news/uk/po ... 22651.html