Camper wrote:

Being relatively new to motor boating I intend to take some boat
handling training but wonder whether I'm being realistic & responible
enough intending to be able to handle a 25 ft motor vessel single
handed as far as mooring, etc is concerned.

Fact is, the bigger and heavier a boat is, the easier it is to handle -
provided your are never in a hurry. 25ft Might actually be too small for
one person to handle if there is some wind to deal with.