The earth's magnetic pole has "wandered", to a measurable extent ever since map makers first started being concerned with a grid for position reference purposes. The reference grid is arbitrary and more about clear communication than correctness about where compasses say north is. Hence your Ordnance Survey map shows a small chart of how to relate magnetic north, true north and grid north. With it is a comment about how many degrees and whether eastwards or westwards, magnetic north is expected to drift in the next five years.
When the pole-flip does occur, it may take decades to fully reverse and there may be years of annoying random wandering in the interim. We have satellites and GPS now so serious users of navigation equipment will not likely be affected. Some ramblers, in serious wilderness settings may get into difficulty when their phone battery goes flat but they'll soon adapt to using sun and stars for alternative directional guidance.
Migratory birds might be badly affected but it is only weakly proved that they are dependent on sensing earth's magnetic field, so take that with a pinch of salt.