Whenever I read it I imagine to myself Emma desperately trying to ignore her.....

I'm preparing the Emma Gazetteer with Farah (literally as we speak) and we both enjoyed putting this quote on the Oxford and Bath pages.

For those not familiar with the geography of Britain here is a map (from 1812) which shows where the counties are, so that you can share the joke:

I think a likely route for Frank to travel south from Yorkshire could have been through the following counties:

Derbyshire
Warwickshire
Oxfordshire
Berkshire and then on to Surrey.

Bath was in Somersetshire( 17 miles north east of Wells).......as far west from Surrey as one could go before hitting the Severn Channel. It wouod ahv been one heck of a diversion.

So, yes you are right: Harriet is probably as geographically challenged as Mrs bennet;-)