oh yes indeedy, heres mine, been living on it for 5 years nowvr666m said:Right.
A Narrow boat has a beam (width) of 6'10", as Nige has already said.
The Narrowest locks that you will find are 7' wide.
Some canals like the Grand Union Canal (London to Birmingham) have 14' wide locks as they were designed so boats could travel 2 abreast (thus doubling the cargo capacity).
Some canals are different (Manchester Ship for example), but the main canal system conforms to these dimensions:
Lock Length: 72'
Lock width: 14' widebeam, 7' narrowbeam
The maximim length of a narrow boat is 70' (to allow for space in the lock).
Some Canals have shorter locks, but the large proportion are as above. Some canals also have turing areas that are not suited to longer boats, but again, most are.
A Narrow boat is the best way forward IMHO, as it means that you can go most anywhere, including the sea (if you are mad )