Please could give me any advice you may have on how to get from Hahn Airport to Aschaffenberg using bus, train and/or taxi?
There is a third rate airline that flies from Hahn to the London area. Take that to England, then go to Heathrow or Gatwick and fly a legit airline to FRA. From FRA take the S-Bahn to Frankfurt Hbf or to Hanau. You can catch a regional train from there to Aschaffenberg.
There is also a dedicated bus from Hahn to Frankfurt Hbf. Takes about 2 hours.