No you need to determine where the leak is and fix the problem. What they are proposing is a bandaid and the problem will get worse as the water will still get in. If the people you hired to do the work cannot figure it out then you need to hire someone else ti find the leak. Don't forget water is funny the leak could actually be on the opposite side of the building from where it is showing up.

I'm with millworkman, need to find the root cause before any problem can be solved. I see you are in the UK. I believe you have what we refer to here in North America as a glass sunroom, conservatory being a style that is popular in the UK. You refer to the water coming " through" the floor. Do you mean to say it appears to be coming up from below or water appears on the floor.
As someone who was in the sunroom/ conservatory business here in Canada I can tell you most likely one or more glass panels are leaking. We have seen water pool in one area on the floor from leaks in the roof panel(s).
A leak test must be done on the entire room.