Thank you all for all your responses. I'm OK on the canals, being born in there Black Country (More canals than Venice, they say), and I've done the Llangolen Canal a number of times on a 45 foot narrowboat, I love Llangollen, it's a beautiful walk from the marina to the beginning of the canal.
Also I used to live on a narrowboat (albeit nearly 40 years ago).
However, I have never done that rout, or that far, and I think it's important to get the facts right.
It was a very silly mistake not to check the size of the boat, and that's what research is for.
Thank you all for your help, my MC will now make it without annoying any of you knowledgeable people in the process.
Does anyone know, what a second hand 55 foot narrowboat would have cost in the mid 1990's, basic boat, mechanically sound, no inside or layout needs be considered as it would be a customised layout.
Thanks again