"Question Author
Morning 158. That's not true at all! The whole idea of the restoration is to allow boats to go from Saul Junction to Lechlade on the Thames. The canal will use the same bridge under the M5 as the River Frome. It's wide enough for us to move the river over a bit and put the canal in alongside it, but a wee bit higher. It will take narrowboats and some cruisers with no trouble at all. cotswoldcansls.com will take you to the website and you can see for yourself. :o} "
Found quite a bit of info on the website but unfortunately nothing about headroom under the M5, are you able to give me a more direct link?