We are not talking about a southern wall, these people come in to legally apply for refugee status. We are talking about a wall to block illegal immigrants that are soon coming from the north. One thing Britain has made very clear is that they don't like immigration, and Europe needs to respect that, like Theresa May respects it as she continues with the Brexit.
As a Brexit deal becomes more and more unlikely, the loss of our European comrade is big. But if you love him you let him go. As this will likely ruin the British economy, there may be a lot of economic migrants jobless in their own country coming from Britain to Europe. As Britain is very safe non of them will be refugees, hence respecting the decision of Britain from the Brexit referendum we may not allow immigration from or to Britain to happen (probably mostly from).
Judging from our expert in immigration, Trump, we need to therefore build a wall through Ireland and need to do tight boarder patrols on the northern beaches of France. To do this we will need funding we have to cut from boarder patrols in the south and hence allow in more legal immigration. Otherwise we can shut down the government if we still need money. Also coming from our American expert we will need to have ICE police searching for British in Europe that have not completed their visa application by the Brexit date.
Show respect to your British comrades and close that boarder for good!