You still need a decent signal to receive digital broadcasts so it is unlikely to work. If you have an aerial on the roof now and you transfer so that the new aerial is in the loft space, the tiling attenuates (reduces) the signal a lot. You are proably best copying the arrangement that your neighbours have in terms of height of aerial and size (length). If it works for them .........
Difficult to know for sure but I had poor reception being just below a hill. I got in an ariel company who put in a reasonably rage ariel with a mast head amplifier and good quality cable and the result was pin sharp reception and perfect freeview. - cost about �180 as I recall
I'd call a local company and ask what's possible they should have a good idea of what the local conditions are like