I've always used the search by Post Code facility which until recently worked fine, but now it does not even recognise my home Post Code. There were problems with this function some years ago when it gave German locations for UK Post Codes and that was eventually fixed.
This current problem means there is no quick and convenient way of searching for caches in the area I expect to be visiting as the suggested workarounds are very long winded compared to just inputting the local Post Code.
I am mindful that as a basic member I'm not really in a position to complain about a free service, but I am surprised that members who pay for the privilege of Premium membership can accept that dependance on external third parties providing this data makes this an acceptable situation which may or may not get fixed at some future point in time.
The best solution for me is to use the excellent(and free!) c:geo application on my Android device as it seems to me to have much better functionalty than the Geocaching.com website and app when out in the field although I would prefer to use my desktop PC when planning trips if only the search facilities worked better.