Hi. I am new to this site also. Have never been to the UK but want to go someday. I guess you have a 29 gal
, or at least thats what my math says. I think your pleco will be fine health wise for now. I had one that got to be 10" in a 29. The problem being that in his wilder moments he was tearing up my tank. Finally gave him to someone with a bigger tank.
But they are extremely hardy. Here in Kansas we are facing problems with them being found in our rivers. Foolish hobbyists tossing them in. They have found some that were 3 feet long. But they are bad for our rivers.
Hope your tank will settle down and be happy forever more, and again...Welcome.