So your example is with a country that doesn't have an FTA with the EU?
I am simply pointing out that across the world all countries seek to protect what they see as their vital interests, including the EU and the UK. In most cases this amounts to protectionism of some kind for certain industries /services and the only way to try to create a so called
level playing field is via some form of protectionism that stops others entering your market, whether that be on price, on quality, on health & safety whatever reasons, your
level playing field only relates to those things you want it to relate to, and to those countries you want to do business with and its effectively a quid pro quo arrangement.
However in essence this is nothing new in various forms it has existed almost since the first trade deals were ever struck. A
'level playing field' implies some kind of 'fairness' exists, but only to those deemed eligible to enter 'the field' You ask some of the third world countries what they think about 'level playing fields'.
If you are a small country but relatively prosperous, say like Ireland, and already
on the field, then clearly you would be mad to want to leave/alter the field . If however you are a large country, but impoverished and can't get on to the field, or even be allowed in some circumstances to approach the
gate to the field, then you want to look to somewhere else to do business. This is where the UK will want to seek alternative business outside the EU, so why should it be a threat to the EU? The only reason being that the UK would now be perceived as a threat to the
protectionism of EU, even when it would be dealing with countries who are currently, not even allowed to beg at the gates of the EU!