It is not overstating the case to suggest that the Wash and its rivers offer access to inland cruising in much the same way as do the ports of mainland Europe. The Netherlands in particular. Always assuming it’s in the right boat!
Inevitably air draft will be a consideration but the UK’s extensive canal and river network and the towns and cities beyond await anyone making a Wash landfall.
Via the River Great Ouse to Cambridge for example. The River Nene to Peterborough and the Grand Union Canal. The River Witham to Boston and Lincoln, connection to the River Trent and onward to York. Not to mention the beauty of the Norfolk Broads via Great Yarmouth or Lowestoft.
For planning, consult a variety of excellent nautical publications from Imray.