Leak??

[mickeyg]

I have observed dampness on the carpet in my hallway and a musty smell which together with "bubbling" of the paint on the wall near the floor leads me to suspect I have an underfloor leak.
If it is a leak how big a job might it be to repair or more importantly what kind of tradesman should I contact to confirm that indeed I do have a leak and to do the necessary work?

 

[ajsnr1]

where exactley is the dampness in relation to the halldoor or perhaps the bathroom if it is near either it could just be water seeping in under the floor because of bad seals or dpc