travel from St Ives in Cornwall to Derwentwater in the Lake District

About 9 hours of train, changing in St Erth, Plymouth and Birmingham to "Oxenholme for the Lake District" and then more time on a bus to Keswick, then a boat, perhaps. You need to leave early in the day. The last train connection to Oxenholme for the Lake Distict leaves St Ives at 12:30, getting to the station after 9pm. If you want a bus it would look like the earliest at 8:15, arriving at 17:22 would be your only hope but even that may be too late. By car you would be talking 8 or 9 hours door to door.

The first train you could take departs St. Ives at 08:15. You will connect in St. Erth, Birmingham and Preston, arriving at Oxenholme Lake District at 17:43. That train goes on to Windermere, arriving at 18:08. On weekdays the last bus (#555) from Windermere to Keswick departs at 18:09 and arrives at 19:07. Perhaps the bus will wait for the train if it is late, but I don't know if that's true. To find out, you could send an e-mail to the Cumbria County Council. The address is [email protected].