An exclusive re-examination of historical lyrics has narrowed down the area the Proclaimers were heading to in their 1988 smash I'm Gonna Be (500 Miles), suggesting the brothers may have been travelling as far afield as Iceland or Portugal in pursuit of the person they both appear to be unreasonably obsessed with.
The initial 500 mile walk could've taken them to all of the UK and parts of northern France, while the "500 more" extends the destination search radius to Sweden, Poland, Spain and parts of Italy. They're going to need two pairs of extremely sound walking boots.
However, as miserabilists on the internet have already pointed out, the map doesn't take into account road curvature, or the fact that not even the Proclaimers can walk over the sea to get to Iceland or France, and the song makes no mention of flights or ferry connections. Plus the Channel Tunnel wasn't open in 1988 so they couldn't have sneaked through the service tunnel on foot, either.